Minots Ledge off Boston Harbor : showing the proposed site of a light house

Beneath Our Feet: Mapping of the features beneath the ocean’s surface began in Europe in the late-16th century, with cartographers using simple symbols such as soundings (numbers that indicate depth in fathoms) and stippling (small dots) to illustrate shallow banks or ledges. The United States established the Coast Survey in 1807 with a mission to map the coastal waters of the nation. The chart of Minot’s Ledge in Massachusetts Bay displayed here was produced by the Coast Survey during its first fifty years, to plan for a lighthouse. The chart displays a number of soundings and profiles, and illustrates sunken rocks, ledges, and the sea floor using a variety of symbols.
Courtesy of Boston Public Library