Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.
Q: Passage: In 1900, Tesla was granted patents for a 'system of transmitting electrical energy' and 'an electrical transmitter.' When Guglielmo Marconi made his famous first-ever transatlantic radio transmission in 1901, Tesla quipped that it was done with 17 Tesla patents, though there is little to support this claim. This was the beginning of years of patent battles over radio with Tesla's patents being upheld in 1903, followed by a reverse decision in favor of Marconi in 1904. In 1943, a Supreme Court of the United States decision restored the prior patents of Tesla, Oliver Lodge, and John Stone. The court declared that their decision had no bearing on Marconi's claim as the first to achieve radio transmission, just that since Marconi's claim to certain patents were questionable, he could not claim infringement on those same patents (there are claims the high court was trying to nullify a World War I claim against the U.S. government by the Marconi Company via simply restoring Tesla's prior patent). Question: When was Marconi's radio demonstration?
A: 
1901