Indigo Lake or simply Indigo is a lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 lying ten miles southeast of central Sitka

Sitka City and Borough, Alaska

The City and Borough of Sitka, originally called New Archangel under Russian Rule, is a unified city-borough located on Baranof Island and the southern half of Chichagof Island in the Alexander Archipelago of the Pacific Ocean , in the U.S...

, on the western coast of Baranof Island

Baranof Island

Baranof Island, also sometimes called Baranov Island, Shee or Sitka Island, is an island in the northern Alexander Archipelago in the Alaska Panhandle, in Alaska. The name Baranof was given in 1805 by Imperial Russian Navy captain U. F. Lisianski to honor Alexander Andreyevich Baranov...

 in the Alexander Archipelago

Alexander Archipelago

The Alexander Archipelago is a long archipelago, or group of islands, of North America off the southeastern coast of Alaska. It contains about 1,100 islands, which are the tops of the submerged coastal mountains that rise steeply from the Pacific Ocean. Deep channels and fjords separate the...

 of Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

 at 57°00′50"N 135°03′53"W.

The name was reported in 1954 by local Sitkan Robert N. DeArmond to the USGS

United States Geological Survey

The United States Geological Survey is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it. The organization has four major science disciplines, concerning biology,...

 and was so named because its intensely and mysteriously indigo

Indigo

Indigo is a color named after the purple dye derived from the plant Indigofera tinctoria and related species. The color is placed on the electromagnetic spectrum between about 420 and 450 nm in wavelength, placing it between blue and violet...

 blue color. The lake about eight tenths of a mile across and long (a circular shape) with very steep and cliffed walls.

The southern ridge of Indigo Lake plays an important part in the trail to Peak 5390

Peak 5390

Peak 5390 is the highest peak on Baranof Island and the Alexander Archipelago which are located in southeast Alaska. Peak 5390 is an informal name, named after the peak's height in feet, but is unnamed by USGS maps. Peak 5390 ranks as the highest island-based peak in the U.S...

.