It is still possible to drive over the Hoover Dam. The new highway that will bypass the dam should be finished by 2008 and it's an amazing sight to see them building this new highway in the canyon.
We crossed it in our motor home and had to stop for Homeland Security police to search all the storage bins and come inside for an inspection. Commercial buses and trucks are not allowed to cross anymore and must use an alternative route.
You can still take tours of the dam and take photos but everyone has to pass through an inspection station. Gone are the hard hat tours that took you deep into the interior of the dam.
The dam was built from 1931-1935 and came in under budget and ahead of schedule. 96 men lost their lives building the dam. It provides electricity for California, Nevada, and Arizona.