From The Atlantic:
Late one night in the summer of 1977, a large radio telescope outside Delaware, Ohio intercepted a radio signal that seemed for a brief time like it might change the course of human history. The telescope was searching the sky on behalf of SETI, the Search for Extraterrestrial Intelligence, and the signal, though it lasted only seventy-two seconds, fit the profile of a message beamed from another world.
The story of the Wow! signal is fascinating if you haven’t heard it. I think they used it as a minor plot point in an episode of The X-Files once upon a time.