Searles Dry Lake

Searles Lake
Searles Lake playa bounded by the Argus and Slate Mountains
Location	Searles Valley, Mojave Desert San Bernardino County, California
Coordinates	35°45′35″N 117°20′07″W / 35.7598°N 117.3353°W / 35.7598; -117.3353Coordinates: 35°45′35″N 117°20′07″W / 35.7598°N 117.3353°W / 35.7598; -117.3353
Type	Endorheic basin
Primary outflows	Terminal (evaporation)
Basin countries	United States
Max. length	19 km (12 mi)
Max. width	13 km (8.1 mi)
Shore length1	50 km (31 mi)
Surface elevation	493 m (1,617 ft)
Settlements	Trona, California
References	U.S. Geological Survey Geographic Names Information System: Searles Lake
1 Shore length is not a well-defined measure.

Searles Lake is an endorheic dry lake in the Searles Valley of the Mojave Desert, in northwestern San Bernardino County, California.

The mining community of Trona is on its western shore. The evaporite basin is approximately 19 km (12 mi) long and 13 km (8.1 mi) at its widest point, yielding 1.7 million tons annually of industrial minerals within the basin to the Searles Valley Minerals mining operations. Searles Lake is bounded by the Argus and Slate Mountains.

The stratigraphic record at Searles Lake shows that it once held brackish water as deep as 200 m (660 ft). Fluctuations in lake levels correspond to the advances and retreats of glaciers in the Sierra Nevada Range. Thirty major lake levels occurred during the last 150,000 years, represented by a sequence of salt and mud beds. The precipitation of minerals occurred during long periods of lake evaporation.

The lake is home to the Trona Pinnacles, a spectacular geologic tufa formation and a National Natural Landmark.

Borax was first produced from the dry lake surface in 1873 by John Searles under the name of the San Bernardino Borax Mining Company. Searles was the first to haul borax using the famous 20 mule team wagons. In 1873, before the railroad was built to Mojave, refined borax was hauled 175 miles by 20 mule teams from Slate Range Playa (now called Searles Lake) to the harbor at San Pedro. The Searles Lake borax discovery has been designated as California Historical Landmark #774, with a plaque at the roadside rest area in Trona. From 1922 to 1928 the Epsom Salts Monorail crossed the Searles Lake on a wooden trestle.