The Washington Monument is an obelisk on the National Mall in Washington, D.C., built to commemorate George Washington, a Founding Father of the United States, victorious commander-in-chief of the Continental Army from 1775 to 1783 in the American Revolutionary War, and the first President of the United States from 1789 to 1797. Standing east of the Reflecting Pool and the Lincoln Memorial, the monument is made of bluestone gneiss for the foundation and of granite for the construction. The outside facing consists, due to the interrupted building process, of three different kinds of white marble: in the lower third, marble from Baltimore County, Maryland, followed by a narrow zone of marble from Sheffield, Berkshire County, Massachusetts, and, in the upper part, the so-called Cockeysville Marble. Both "Maryland Marbles" came from the "lost” Irish Quarry Town of "New Texas". It is both the world's tallest predominantly stone structure and the world's tallest obelisk, standing 554 feet 7+11⁄32 inches (169.046 m) tall, according to U.S. National Geodetic Survey measurements in 2013–2014. It is the tallest monumental column in the world if all are measured above their pedestrian entrances. It was the world's tallest structure between 1884 and 1889, after which it was overtaken by the Eiffel Tower, in Paris. Previously, the tallest structures were Lincoln Cathedral and Cologne Cathedral.

An obelisk is a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape or pyramidion at the top. Originally constructed by Ancient Egyptians and called tekhenu, the Greeks used the Greek term obeliskos to describe them, and this word passed into Latin and ultimately English. Though William Thomas used the term correctly in his Historie of Italie of 1549, by the late sixteenth century, Shakespeare failed to distinguish between pyramids and obelisks in his plays and sonnets. Ancient obelisks are monolithic and consist of a single stone; most modern obelisks are made of several stones.