text: Formed by the retreat of the glaciers at the end of the last Ice Age, Frame Lake remained a relatively pure lake even as the area was settled and modern development impinged on it. The closure of its only outlet around 1970, however, led swiftly to its decline and eutrophication. By the end of the 20th century it could no longer support fish and was not being used for primary recreational purposes. Attempts to revive it started in the 2010s.