Washington Monument http://bensguide.gpo.gov/3-5/symbols/wa_monument.html
Jefferson Memorial http://en.wikipedia.org/wiki/Jefferson_Memorial
Mount Rushmore http://bensguide.gpo.gov/3-5/symbols/mountrushmore.html
Ben's Guide to U.S. Symbols http://bensguide.gpo.gov/k-2/symbols/index.html
Lincoln Memorial http://bensguide.gpo.gov/3-5/symbols/lincoln.html
The White House http://bensguide.gpo.gov/k-2/symbols/whitehouse.html