The matte painting of the destroyed Capitol building was painted by Michelle Moen, one of the best painters I've ever seen, and just so much fun to work with. I gave her a tight architectural perspective drawing from which to work. The foreground debris and the dome itself are miniature elements for which I supervised the plate photography to make sure that it would all hook up with the layout and the live plate. The elements were composited in Composer.
The Mount Rushmore shot was painted by me. It started out as a daylit 4x5 positive, which I turned into night using Photoshop. I then painted in the heads. To create the smoke, Mike Fink used diatomacious earth (I probably misspelled that...) blown through hoses, with miniature boulder aggregate mixed in.
In addition to the various matte paintings, I also painted production illustrations for the opening sequence, one of which is in the stills section of this site.