In 1884, I decided to leave Europe, realizing that my revolutionary invention was not receiving the support it deserved. With a recommendation from Charles Batchelor, a close associate of Thomas Edison, I arrived in New York in June of that year. On the note Batchelor gave me, he had written: “I know two great men. One is you, and the other is this young man standing before you.” I worked at Edison’s company for a short time, but our differing views on technology, particularly regarding direct current and alternating current, led to my departure.

In early 1885, I founded my first company, Tesla Electric Light and Manufacturing, in New York. By 1887, I had launched a new company, Tesla Electric Company, to apply my inventions in the field of polyphase alternating currents. In my laboratory, I constructed the first polyphase induction motors and generators, initiating a revolution in electrical engineering.

In 1888, the U.S. Patent Office approved my core patents for the polyphase system, including the “Electromagnetic Motor” (No. 381,968) and “Electrical Transmission of Power” (No. 382,280). Between 1888 and 1891, I secured a total of 36 patents, laying the groundwork for the Second Industrial Revolution.

In 1889, I returned to Europe for the first time since my departure to America. During this visit, I toured my homeland, saw my mother and sisters in Gospić, and attended the World’s Fair in Paris. As a member of the American delegation of electrical engineers, I participated in the International Congress of Electricians, where I presented my ideas and innovations.

By 1890, I had begun researching high-frequency currents, which would define my work throughout the 1890s. In 1891, I invented the oscillatory transformer, now known as the Tesla coil, for which I received a patent on June 23. That same year, on July 30, I became a naturalized U.S. citizen.

In 1892, I returned to Europe for the second and final time. During this extended visit, I traveled to London, Paris, Budapest, Zagreb, Belgrade, and spent time with my family in Lika.

The journey began in early February in London, where I delivered two lectures on my experiments with high-voltage, high-frequency alternating currents. I gave the first lecture on February 3 at the Institution of Electrical Engineers and the second the following day at the Royal Society of Great Britain. A few weeks later, I repeated these lectures in Paris before members of the Society of Physicists and the International Society for Electrical Engineering, marking my triumphant return to the “City of Light.”

In Paris, I spent over a month before receiving news that my mother, Đuka, was gravely ill. I immediately set off for Gospić, where I was able to see her one last time before she passed away on April 16, 1892.

In June of the same year, at the invitation of the Belgrade Municipality delegation and the Association of Engineers, I visited Belgrade for the first and only time. I spent 31 hours there, staying at the “Imperial” hotel. I toured Kalemegdan Fortress and the National Museum, and at the Grand School, I gave a lecture on my latest research and inventions. Prince Aleksandar Obrenović received me with great honor, and by royal decree, I was awarded the Order of Saint Sava, Second Class—my first official recognition for scientific work.

When I arrived in America in 1884, electrification based on direct current was still in its infancy. Many scientists were working on improvements in arc lighting and direct current generators. During my time at Thomas Edison’s company, I, too, was compelled to work with direct current generators.

After leaving Edison’s company, I focused on arc lighting and secured seven patents in this area. However, I was convinced that the future lay in alternating current systems. This conviction proved correct after years of hard work and intense rivalry between two opposing concepts—direct current and alternating current. This struggle, famously known as the “War of Currents,” saw Edison’s company advocating for direct current on one side and George Westinghouse, who recognized the advantages of my ideas and purchased my key patents for the polyphase system, on the other.

Our joint triumph became evident when the decision was made to power the 1893 Chicago World’s Fair with alternating current. On May 1, thousands of light bulbs illuminated the exhibition’s pavilions, delivering a decisive blow to Edison’s system. This fair, dedicated to the 400th anniversary of America’s discovery, was lit using 12 of my two-phase generators, earning Chicago the nickname “City of Light” during the exhibition.

In October of the same year, the International Niagara Commission decided to entrust the construction of a system to harness the power of Niagara Falls to companies that proposed my polyphase system. This decision marked a significant leap forward in electrification and validated the correctness of my vision.

In 1894, I was elected a corresponding member of the Serbian Royal Academy. This was one of the first significant recognitions of my scientific and inventive work. However, it wasn’t until February 16, 1937, that I was unanimously elected a full member of the Academy.

The following year, on March 13, 1895, a devastating fire engulfed the building at 35 South Fifth Avenue in New York City, where my laboratory was located. This fire destroyed all prototypes of my machines, hundreds of original light bulbs, books, letters, and invaluable technical documentation. Despite this tremendous loss, it became a catalyst that strengthened my resolve to continue my work.

The night of November 15-16, 1896, marked a historic moment for science and energy. It was then that the first large alternating current hydroelectric power plant, built on the Niagara River, was put into operation based on my patents. Out of the 13 patents used for its construction, nine were mine. The first kilowatt-hours of electricity generated by this plant were transmitted to the city of Buffalo, 32 kilometers away. This project was a turning point in the development of industry, enabling rapid progress in the generation, transmission, and use of electricity by the late 19th century. I believe my contributions in this field inspired later advancements in energy.

My thoughts on energy were published in the magazine Century in 1900, in an article titled “The Problem of Increasing Human Energy.” In this work, I argued that humanity should abandon “barbaric” methods of energy production, such as burning coal and oil, which deplete natural resources. Instead, I advocated for the use of sustainable energy sources, including waterfalls, sunlight, wind, tides, waves, and the energy derived from temperature differences in the Earth or oceans. My vision of clean and renewable energy remains highly relevant today, reflecting my belief in science serving the well-being of humanity.

In 1897, I made significant advancements in radio technology by building a new, larger radio station near New York City. I successfully transmitted radio signals over a distance greater than 40 kilometers, laying the groundwork for modern radio communication. I filed two key patents: System of Transmission of Electrical Energy (No. 645,576), which describes a system with four resonant circuits tuned to the same frequency, and Apparatus for Transmission of Electrical Energy (No. 649,621), which defines the radio apparatus.

In 1898, I demonstrated the operation of my remote-controlled boat at the first exhibition of electrical devices in Madison Square Garden. Using radio waves, I controlled the movement of a model boat remotely, astonishing the audience and showcasing a groundbreaking innovation. On July 1 of that year, I filed a patent titled “Method of and Apparatus for Controlling Mechanism of Moving Vessels or Vehicles” (No. 613,809), which was granted on November 8. Aware of its importance, I secured this patent in 11 countries, laying the foundation for the future development of remote-controlled devices.

My research into high-frequency currents and high voltages began in 1888 and marked a significant phase of my scientific career. These studies not only contributed to energy systems but also found applications in fields such as wireless telegraphy, radio technology, medicine, and lighting. The first significant results with high-frequency current generators were achieved in 1891 at Columbia College. That year, I patented my oscillating transformer, known today as the Tesla Coil, under patents No. 454,622 and 462,418.

The oscillating transformer enabled not only the generation of high-frequency currents but also a significant increase in voltage through the principle of resonance. I achieved remarkable voltage increases, reaching millions of volts. My research in this area culminated in the construction of my famous laboratory in Colorado Springs in 1899. I spent a year there conducting groundbreaking experiments, including the discovery of the Earth’s stationary waves, one of the greatest achievements of my career.

In 1899, I moved to Colorado Springs to conduct experiments that led to new discoveries in high-frequency currents. I arrived on May 18 with the goal of constructing a powerful high-frequency current generator, refining methods for individualization and mutual isolation of transmitted energy, and determining the laws governing the propagation of currents through the Earth and atmosphere. From June 1, 1899, to January 7, 1900, I meticulously recorded detailed notes on my experiments, including measurements, calculations, diagrams, and observations about new configurations of instruments and devices.

In 1900, I published an article titled “The Problem of Increasing Human Energy” in Century magazine, edited by my friend Robert Underwood Johnson. This article garnered significant attention for its exploration of energy as a key aspect of civilization’s progress.

Between 1901 and 1902, I constructed a laboratory and transmission tower on Long Island as part of a project known as the “World Wireless System.” Designed in collaboration with renowned American architect Stanford White, the project aimed to transmit signals wirelessly through the Earth, which acts as a conductive medium, to be received anywhere on the planet. Although the tower was completed in 1902, it never achieved its originally envisioned form.

Between 1903 and 1906, I faced numerous challenges in completing my World Wireless System project. Financial support from my principal investor, John Pierpont Morgan, ceased. Despite numerous letters urging him to continue funding, I had to abandon the project. In 1906, I left Long Island and redirected my focus to mechanical engineering research.

On April 18, 1905, I patented the “Art of Transmitting Electrical Energy Through the Natural Mediums” under patent number 787,412. This patent, which I filed on May 16, 1900, described the phenomenon of standing waves, which I determined could propagate in all directions across the Earth. My intention was to confirm and expand upon ideas regarding the Earth’s resonance, with expectations that the resonant frequencies would be at 6, 18, and 30 Hz.

In 1907, I realized the first working model of a bladeless turbine, a significant milestone in my mechanical engineering endeavors. I developed an original principle of fluid propulsion, which I applied to pumps, turbines, compressors, and ventilators. The concept for this invention had been conceived as early as 1890 and took shape by 1902. On June 1, 1906, I presented this principle to experts, and in 1907, I applied it practically. My turbine utilized a rotor with parallel disks, simplifying the design and improving efficiency while reducing the number of components.

Following the financial difficulties that arose from the failure on Long Island, I turned to mechanical engineering in search of an invention that would be both accessible and straightforward for industrial use. In 1908, I began collaborating with the American and British Manufacturing Company, owned by John H. Hadley. I worked on marine propulsion systems until 1911. In 1909, I founded the Tesla Propulsion Company, aiming to commercialize my mechanical inventions. The company’s headquarters was located at 165 Broadway in New York City.

In 1913, I filed a patent for a fountain design inspired by my collaboration with Louis Comfort Tiffany, the renowned artist and designer. I developed several fountain models that utilized the circulation of large volumes of water. Although I patented the fountain in 1914 and invested considerable effort into this project, it did not achieve significant commercial success. Nevertheless, this invention was another attempt to confront challenges and address my financial difficulties during that time.

In 1914, I opened a new office in the Woolworth Building, located at 233 Broadway in New York City. At the time, this building was the tallest in the world, a symbol of modern architecture and progress. The space was highly prestigious, reflecting my aspirations. However, due to significant financial difficulties, I was forced to vacate the office after only a few months, marking another challenge in my relentless pursuit of scientific advancements.

In 1915, I published my first autobiographical article, titled “Some Personal Recollections,” in Scientific American. This piece offered the public a rare glimpse into my life and inventive journey. I reflected particularly on the moment that shaped my career—the discovery of the rotating magnetic field principle in Budapest in 1882. The article received widespread attention and allowed me to share the inspirations and methods that underpinned my scientific path.

By 1916, I managed to monetize one of my inventions by selling the license for my “Speed Indicator” patent to the Waltham Watch Company in Boston. This company produced approximately 60,000 speedometers, primarily for mass-produced automobiles, up until 1921. While this achievement provided some financial relief, it was insufficient to resolve my broader economic challenges. Nevertheless, I continued to pursue my innovations and sought opportunities to realize my visions.

Around this time, I met Archimandrite Nikolaj Velimirović in New York through my friend, Professor Paja Radosavljević. Nikolaj was working to unite the Serbian community in America to support Serbia during World War I. These discussions were significant, but tensions between me and Mihajlo Pupin, coupled with Professor Radosavljević’s critical stance toward Pupin, prevented us from issuing a unified declaration. Nikolaj later expressed regret for attempting to involve me in national affairs, believing my scientific work to be of greater importance to humanity.

In 1917, I gave an interview to Electrical Experimenter magazine, published in August, four months after the United States entered World War I. In this interview, I outlined my concept for a device that would later become known as radar. I described the potential use of electrical waves for detecting and neutralizing submarines—a revolutionary idea at the time. This vision was part of my lifelong commitment to creating inventions that could enhance safety and advance conditions for humanity. My concept for radar demonstrated a profound understanding of the capabilities of electromagnetic waves and their future applications in technology.

On May 18, 1917, I was awarded the Edison Gold Medal, the highest recognition of the American Institute of Electrical Engineers. Although the medal was established in 1904, it was officially granted to me on December 13, 1916, for my work in the field of polyphase and high-frequency currents. The formal ceremony took place at the American Institute of Electrical Engineers in New York. Ironically, during this period, I was struggling financially, residing at the Waldorf-Astoria Hotel in a deferred-payment apartment. Due to a debt of $20,000, the hotel owner, George Boldt, assumed ownership of Wardenclyffe and began dismantling my famous tower, selling off the land.

In 1918, I began a collaboration with the “Allis-Chalmers” company, one of the largest manufacturers of steam turbines. Our goal was to develop and test my steam and gas turbines. Over the next two years, two of my turbines, with capacities of 200 and 500 kilowatts, were tested. Unfortunately, the results were unsatisfactory, which I attributed to inadequate working conditions, and the partnership was ultimately terminated.

In 1919, I published my famous autobiography, My Inventions. This series of articles appeared in six installments in the magazine Electrical Experimenter, edited by my friend Hugo Gernsback. Through these texts, I described my visions, unique thought processes, and methods of work, as well as various experiences from my life. I also detailed my experiments, including research on the effects of electrical currents of specific frequencies on the human body, which I often tested on myself. Additionally, I described my extraordinary sense of hearing, which was several times more sensitive than average.

Between 1921 and 1925, I collaborated with Edward J. Budd’s company, a manufacturer of automobiles and engines. During this partnership, I proposed the production of a new type of automobile engine based on my original concept. My idea was to introduce revolutionary changes to the automobile industry, but unfortunately, the project never fully materialized.

In 1923, I filed two patents in the field of chemical technology. These patents, titled “Process for Processing and Transporting Sulfur” and “Apparatus for Processing and Transporting Sulfur,” were registered under numbers 645,568 and 645,569 on June 15 of that year. The examination process lasted several years, and after minor corrections required by the Patent Office, the patents were granted to me in June 1926. However, due to the non-payment of the prescribed fee within the legal deadline, the application was withdrawn.

In 1927, I lived on the fifteenth floor of the Pennsylvania Hotel in New York City, in room 1522E. I led a solitary life, paying close attention to my diet and overall health.

In 1928, at the age of 72, I received what would become my final patent, a culmination of my lifelong dedication to science and invention. Patent No. 1,655,114, titled “Method and Apparatus for Aerial Transportation,” represented a revolutionary concept for an aircraft capable of vertical takeoff and landing—a hybrid of a helicopter and airplane powered by my advanced turbines. This invention was yet another testament to my vision of the future and unwavering belief in the power of science and technology.

At the Electric Appliance Exhibition in Madison Square Garden, I conducted an experiment that captivated the audience. Using radio waves, I demonstrated remote control of a model boat, showing for the first time the potential to control a device without any physical connection. I called this invention the “teleautomaton,” which I viewed as a precursor to modern robots. Its design was inspired by the human body and mind, mimicking our ability to respond to external stimuli. Commands were transmitted via radio waves of a specific frequency from the remote control to the boat’s antenna, calibrated to receive those signals.

In subsequent iterations, I improved the device by enabling it to receive two distinct signals simultaneously. This innovation ensured that the teleautomaton would only respond when both signals were registered, thereby enhancing reliability and resistance to interference. Unknowingly, I had laid the groundwork for the logical “AND” circuit, a fundamental concept in modern computing technology.

One of my mechanical oscillators sparked an amusing anecdote. Although it was not intended to cause vibrations, the device, when attached to a support beam of a building, entered resonance and caused tremors throughout the neighborhood. My oscillators were primarily designed to generate electrical currents with specific characteristics, but I also explored their mechanical applications as generators of oscillations. Unfortunately, the 1895 fire destroyed many of these prototypes. While I later rebuilt some, this line of research was foundational for my later ventures in mechanical engineering.

Another of my controversial projects was the concept of “death rays,” or concentrated beams of particles. I explained that even if the entire electrical energy of New York City were concentrated into a beam, it would not harm a person at significant distances. However, a focused particle beam could serve as a powerful weapon. This idea was not a single invention but rather an integration of several groundbreaking technologies. The project drew immense attention during my lifetime, and the mystery surrounding it has endured long after my death.

On my 75th birthday, celebrated on July 10, 1931, I was deeply honored by acknowledgments and congratulations from over 70 prominent figures of my time—Nobel laureates, scientists, engineers, industrialists, and artists. This jubilee garnered worldwide attention, with numerous celebrations and academic events held across Europe and America to honor my contributions to science and technology. That July, it seemed as though the entire world was celebrating alongside me.

One of the most notable gestures came from my young friend, Kenneth Swezey, a journalist from the New York Sun. He compiled a commemorative album containing birthday greetings from my contemporaries, including distinguished scientists such as Albert Einstein, the German physicist; Sir William Henry Bragg, the English physicist; Sir Edward Victor Appleton, the English physicist; Robert Millikan, the American physicist; and Arthur Holly Compton, the American physicist. Among them were also several notable Serbian intellectuals and artists: Milutin Milanković, the Serbian mathematician and astronomer; Ivan Đaja, a professor of physiology at the University of Belgrade; Dragomir Jovanović, a professor of electrical engineering; Uroš Predić, the Serbian painter; Slavko Bokšan, an engineer and founder of the Nikola Tesla Institute in Belgrade; and Nikola T. Perović, the Serbian writer. Swezey managed to gather 75 congratulatory letters, each representing a year of my life. This unique collection, which I treasured until the end of my days, was a priceless keepsake.

This compilation was one of the greatest informal honors I ever received. It testified to the respect and admiration my contemporaries from around the world—scientists, artists, industrialists, and engineers—held for me. The recognition I received through this album, for my work, vision, and achievements, was more meaningful to me than any official award.

That same year, in 1931, on my 75th birthday, my portrait graced the cover of Time magazine. The article highlighted my contributions to systems for the generation and transmission of electrical energy, an acknowledgment I deeply appreciated.

From 1934 to 1942, my life was marked by a series of significant events and some tragic circumstances. In 1934, I published an obituary in The New York Times for King Alexander I Karađorđević, who had been assassinated in Paris. I expressed my deep respect for him as both a leader and a person.

During this period, I also developed the concept of telegeodynamics, a new technology that involved transmitting energy mechanically through the Earth. I offered my innovations to companies such as Texas, Westinghouse, and Buffalo, believing that this system could be applied to navigation, industry, and signal transmission.

In 1935, I signed an agreement with the Soviet trade delegation in New York, represented by the company “Amtorg Trading.” This collaboration aimed to develop a technology capable of creating an impenetrable defensive barrier to protect the Soviet Union from potential enemy aggression. I presented them with the concept of concentrated particle beams, which later came to be known as “death rays.”

The agreement, signed on April 20, 1935, obligated me to deliver detailed plans and technical documentation for a facility to realize this vision within four months. My design proposed a device capable of generating 50 million volts, producing concentrated particle beams that could be projected at least 150 kilometers. These particles would travel at speeds of no less than 50 kilometers per second, with devastating precision and power.

The purpose of this invention was not solely offensive but also defensive, aiming to establish a system that could ensure peace and prevent future wars. I believed this technology could serve as a deterrent, protecting nations from conflict. However, like many of my projects, it faced numerous challenges and was never fully realized. Nevertheless, the idea of directed particle beams remained one of my most ambitious and enigmatic visions.

In 1936, I experienced a car accident in New York when I was struck by a taxi during one of my daily walks. The recovery took six months, but I persevered, continuing my work and research despite the difficulties. I managed to regain my strength and return to my activities.

A particularly significant moment occurred in 1942 when I met King Peter II Karađorđević, who had traveled to Washington to visit the U.S. president. We met in my apartment at the New Yorker Hotel. His visit was deeply emotional, and our conversation left a profound impression on both of us. The King later noted in his diary that the encounter was exceptionally moving, and we both were deeply touched, shedding tears.