The Washington Monument

In 1783, Congress decreed that George Washington deserved a monument as grand as his quest for American democracy and freedom. This decision spurred architect Robert Mills to draw up plans for the Washington Monument, the highest all-masonry tower in the world. Unfortunately, progress wasn't swift: Bureaucratic hurdles and the Civil War impeded the structure's completion until 1885, long after the architect -- and Washington -- had died.

At 55 feet wide at the base and 555 feet tall, the white obelisk on the National Mall is made of 36,000 stones of marble from Maryland (the exterior) and granite from Maine (the interior) with a combined weight of 90,000 tons. One interesting feature is the interior iron stairway with 50 landings and 897 stone steps. These donated stones come from every state in the Union, as well as Native American nations and foreign countries. While the stairwell has been closed since the 1970s, visitors can gain access to the top observation area via elevator.