Blue Mountain Lake is a 1,334-acre lake in the town of Indian Lake, Hamilton County, in the central Adirondacks of New York. It forms the eastern end of the Eckford chain of lakes and lies west of Blue Mountain, with the hamlet of Blue Mountain Lake on its southeastern shore and the Adirondack Museum overlooking it from the east. The lake is about 2.5 miles long, reaches a depth of 100 feet and holds ten islands. It has been a vacation destination since the mid-19th century, when hotels such as the Prospect House of 1881 were built on its shores.