In Washington, D.C., a city steeped in history--from museums and monuments to statues and stations--there are perhaps no structures as prominent as the working symbols of the United States' three-branch government: the White House, the Capitol, and the Supreme Court. Embodying our nation's complex and, at times, tumultuous history, these buildings also house invaluable pieces of our American past. A visit to these national treasures provides a lesson...