Nikola Tesla Dies
Tesla died of heart failure alone in room 3327 of the New Yorker Hotel, on 7 January 1943.
Despite having sold his AC electricity patents, Tesla died with significant debts. Later that year the US Supreme Court upheld Tesla's patent number 645576 in a ruling that served as the basis for patented radio technology in the United States.
Soon after his death Tesla's safe was opened by his nephew Sava Kosanović. Shortly thereafter Tesla's papers and other property were impounded by the United States' Alien Property Custodian office in Tesla's compound at the Manhattan Warehouse, even though he was a naturalized citizen.
Dr. John G. Trump was the main government official who went over Tesla's secret papers after his death in 1943. At the time, Trump was a well-known electrical engineer serving as a technical aide to the National Defense Research Committee of the Office of Scientific Research & Development, Technical Aids, Div. 14, NTRC (predecessor agency to the CIA's Office of Scientific Intelligence). Trump was also a professor at M.I.T., and had his feelings hurt by Tesla's 1938 review and critique of M.I.T.'s huge Van de Graaff generator with its two thirty-foot towers and two 15-foot diameter balls, mounted on railroad tracks—which Tesla showed could be out-performed in both voltage and current by one of his tiny coils about two feet tall. Trump was asked to participate in the examination of Tesla's papers at the Manhattan Warehouse & Storage Co. Trump reported afterwards that no examination had been made of the vast amount of Tesla's property, that had been in the basement of the New Yorker Hotel, ten years prior to Tesla's death, or of any of his papers, except those in his immediate possession at the time of his death. Trump concluded in his report, that there was nothing that would constitute a hazard in unfriendly hands.
At the time of his death, Tesla had been working on the Teleforce weapon, or 'death ray,' that he had unsuccessfully marketed to the US War Department. It appears that Teleforce was related to his research into ball lightning and plasma, and was conceived as a particle beam weapon. The US government did not find a prototype of the device in the safe.
After the FBI was contacted by the War Department, his papers were declared to be top secret. The personal effects were sequestered on the advice of presidential advisers; J. Edgar Hoover declared the case most secret, because of the nature of Tesla's inventions and patents. One document stated that "[he] is reported to have some 80 trunks in different places containing transcripts and plans having to do with his experiments [...]". Altogether, in Tesla's effects, there were the contents of his safe, two truckloads of papers and apparati from his hotel, another 75 packing crates and trunks in a storage facility, and another 80 large storage trunks in another storage facility. The Navy and several "federal officials" spent two days microfilming some of the stuff at the Office of Alien Properties storage facility in 1943, and that was it, until Oct., 1945.
Tesla's family and the Yugoslav embassy struggled with the American authorities to gain these items after his death because of the potential significance of some of his research. Eventually Mr. Kosanović won possession of the materials, which are now housed in the Nikola Tesla Museum.
Tesla's funeral took place on 12 January 1943, at the Cathedral of Saint John the Divine in Manhattan, New York City. His body was cremated and his ashes taken to Belgrade, Serbia, then-Yugoslavia in 1957. The urn was placed in the Nikola Tesla Museum in Belgrade.