The Washington Monument is an obelisk near the west end of the National Mall in Washington, D.C., built to commemorate the first U.S. president, General George Washington. The monument, made of marble, granite, and bluestone gneiss, is both the world's tallest stone structure and the world's tallest obelisk.Designed by architect Robert Mills in the 1840s, construction of the stone obelisk began in 1848, halted at half height in 1856, then resumed from 1876-1884. Achieving a height of 555 feet, the Washington Monument surpassed the Cologne Cathedral as the world's tallest structure–but only briefly. In 1889, the Eiffel Tower asserted the new age of metal construction.[1]