In the film Close Encounters of the Third Kind, how did the government know to build the landing complex at Devils Tower?

If there hadn’t been contact previously, how did the government know the following:

1) the five tone musical passage (and that it was a means if communication)

2) the hand movements and that they would be non-threatening

3) to build the landing area near Devils Tower?

Or is the assumption that there were earlier (first and second kind) communications, years previously, that would have negotiated/instructed the government on where to build?

After all, UFO landing sites take a while to build.