premise: The Washington Monument is the world's shortest obelisk.
hypothesis: The Washington Monument is an obelisk on the National Mall in Washington , D.C. , built to commemorate George Washington , once commander-in-chief of the Continental Army and the first President of the United States . Located almost due east of the Reflecting Pool and the Lincoln Memorial , the monument , made of marble , granite , and bluestone gneiss , is both the world 's tallest stone structure and the world 's tallest obelisk , standing 554 ft tall according to the National Geodetic Survey ( measured 2013 -- 14 ) or 555 ft tall according to the National Park Service ( measured 1884 ) . It is the tallest monumental column in the world if all are measured above their pedestrian entrances . Upon completion , it became the world 's tallest structure , a title previously held by the Cologne Cathedral .