The daybeacon is composed of a rectangular granite block base or platform, which is topped by a truncated, wooden eight-sided pyramid encased in a thin coating of concrete. It is painted black except for a band of white around the middle. The pyramid was originally covered in slate shingles; the concrete was likely applied to the structure sometime between the World Wars. Access to the pyramid is provided by a granite block stairway at the south side of the base. The pyramid's hollow interior contains a mortise and tenon structure, which is supported by cross-members extending from a center column.
In the early 1800s, the Boston Marine Society recognized the danger the disappearing island posed. In December 1803 the Society reported to Congress on the dangerous conditions at Nix's Mate and appealed to Congress to build a wall around what remained of the island on which to place a warning beacon. Congress declined to act and the Commonwealth of Massachusetts purchased what remained of Nix's Mate Island and authorized $3,000 to construct the wall and beacon.
By 1832, the island and improvements were sold to the U.S. government, who began building a stone platform topped by a wooden pyramidal monument. It is likely that stones from the 1805-1806 wall were used in the construction of the platform. In 1841, the wooden pyramid burned after being struck by lightning but was rebuilt.
Today, despite an extensive system of buoys, Nix's Mate remains an important navigational aid in Boston Harbor. It was slated for removal and replacement in 2001. However, after public outcry the U.S. Coast Guard began a major restoration of the daybeacon in 2003 shoring up the stone base in an effort to prevent further erosion.
Nix's Mate Daybeacon is located at the entrance to Boston Harbor. It is best viewed by boat though it can be seen from other Boston Harbor islands including Deer, Lovells and Gallops, which are all part of the Boston Harbor Islands National Recreation Area. For more information see the Boston Harbor Islands Visitor Guide.