Fun little museum! We stayed here a few nights and as hotels guests we were able to get in for free. I saw a sign that said something like $2 per person. Which isn't too bad. Unless you're cheap...
Its full of good info on the area and about Hoover dam. If you're into history like I am this is a place you want to visit before you go to Hoover dam. Will only take about 30 minutes of your time. And you'll help out the humble Boulder city hotel.