Actually, it was originally called Boulder Dam in the building phase but was officially Named Hoover Dam when dedicated. The a-hole FDR changed it to Boulder because that’s the sort of thing a Democrat would do in order to deprive a Republican of any credit for doing something ahead of schedule and under budget. In 1947 it was renamed Hoover and has remained so ever since.
To make it a little worse, it was originally intended to be called Hoover dam, but FDR ordered the name change to spite his enemy, only being renamed just after the 22nd Amendment, limiting presidential terms, was passed.
Things really haven’t changed. There was a bitter fight against naming Ronald Reagan airport in D.C., even involving lots of litigation to prevent it. Then after congress changed hands, the Democrats immediately filed to change its name again, though that went nowhere.