🤔I'm guessing this might have something to do with HOOVER DAM?
Found this on a fast search 💥
"the Colorado River flows into Lake Mead, one of the largest manmade lakes in North America. It began filling upon the completion of Hoover Dam (previously known as Boulder Dam) in 1935."
https://grcahistory.org/sites/beyond-park-boundaries/lake-mead/