What a great dam this is! Great to witness some of the US engineering marvels and you get to be in 2 states at ones with one foot in Arizona and the other in Nevada.
=P
It's a shame the water level is extremely low and affecting the southwest. But just enjoy the sights around the Hoover Dam and read some the history plaques to have some idea and take a tour. I didn't take a guided group tour but the helicopter tour was amazing but expensive!