This 555-foot obelisk (Washington Monument, pictured) was built in honor of the nation's first president, George Washington. Though construction began in 1848, it was not completed until 1884, when it served as the world's tallest building for five short years (the Eiffel Tower's completion topped it in '89). It is still Washington, D.C.'s tallest structure.
Thomas Jefferson, the third U.S. president, wished to make the city an "American Paris" with "low and convenient" buildings on "light and airy" streets. The Heights of Buildings Act of 1910 restricted all buildings to no taller than the width of the street on which they were built.
D.C.'s 68 square miles hold numerous important monuments including the Jefferson Memorial, the Lincoln Memorial, the Korean War Veterans Memorial, the Vietnam Veterans Memorial, the African American Civil War Memorial and many more.