Let use begin at the very beginning. It is believed that Tesla built the first time machine back in the 1800's. He was not a just a great inventor, but possibly the greatest inventor of all time. Most of present technology would not be possible without the great inventions created by that great mind.
In the 1930's the US was building time machines using vacuum tubes no less and then in 1940's this technique was adapted to make a ship disappear called the Philadelphia Experiment. The idea was to make the ship be slightly out of phase with our reality.
This had disastrous consequences for the crew, but the experiments continued with the Montauk Project in the 1980's. This created many problems in our timeline which plague us still.