Here's a nice high-resolution image from Flickr user mins3rdkid showing Lake Mead, on the Arizona/Nevada border. The picture was posted in Flickr's Unknown aerial shots pool. Lake Mead is formed behind the Hoover Dam, which is just out of the frame to the right. In this image, the state of Nevada is in the foreground and upper left; Arizona is in the upper right.
Here's another view of Lake Mead from a similar angle, taken by Flickr user KTdesigner August 2006.
Photos taken: May 9, 2007
Photos by: mins3rdkid