The United States Capitol is the meeting place of the United States Congress.
The Washington Monument is the world's tallest stone structure and obelisk.
The Union Arch Bridge serves both pedestrian and vehicular traffic.
The Bollman Truss Railroad Bridge is a landmark of industrial design and construction.
The Thomas Viaduct is an arched stone railway bridge spanning the Patapsco River between Baltimore County and Howard County.
The Mason-Dixon line is a demarcation line separating four U.S. states.
Philadelphia City Hall is the house of government for the city of Philadelphia, Pennsylvania.