By the beginning of the 19th century, Nixes Mate had eroded to a low rocky shoal which, lying at the head of the Narrows—the main entrance to Boston Harbor at that time—was a navigational hazard. In 1803, the Boston Marine Society asked Congress to build a seawall surmounted by an unlighted beacon around what remained of the island. Congress declined, so in 1805 the state purchased what was left of Nixes Mate and had the wall and beacon built, the latter by Ozias Goodwin (NPS n.d.; Rowlett 2008). In 1832, the federal government finally purchased Nixes Mate and built the existing stone platform, likely using stones from the 1805–06 wall, and a pyramid beacon. That beacon was struck by lightning and burned in 1841, but was soon rebuilt. Today, the beacon is a hollow wooden octagonal pyramid with a light coating of concrete that was probably applied between World Wars I and II (NPS n.d.).