Has the US done anything that huge and kept it secret? The Manhattan project is the only one I can think of, and that involved sequestering the entirety of the

Has the US done anything that huge and kept it secret? The Manhattan project is the only one I can think of, and that involved sequestering the entirety of the nations top physicists, chemists, and metallurgists in the desert and employed 130,000 people. This was before the internet and during a time when Americans were unified in a war effort in a way that hasn't existed before or since.