Gilbert Stanley Underwood designed numerous lovely buildings for the U.S. federal government (most notably for the National Parks Service), somehow slipping by the guardians of mediocrity who usual govern such matters. Probably his most notable building is the Ahwahnee Hotel in Yosemite National Park. His Grand Canyon Lodge on the North Rim is also stunning.
Here are some links. Alas, there aren't many.
Amfac's Grand Canyon Lodge page. These are the folks who now run the place.