Baldwin Lake is a natural, intermittent, alkali lake in a valley of the San Bernardino Mountains, in San Bernardino County, California. The depth of Baldwin Lake's lowest point is approximately 25 feet (7.6 meters). At its widest, the lake is more than a mile across. Chaparral grows on the surrounding terrain. Baldwin Lake is part of the Baldwin Lake Ecological Reserve.
Benjamin Davis Wilson encountered the lake in 1845, while tracking horse thieves in the San Bernardino Mountains. When Wilson saw that the region was populated by many grizzly bears, he divided his 22 men into hunting partners. The men slaughtered 11 bears for the fur pelts. While returning to Jurupa (Riverside), they slaughtered another 11 bears for the fur. Wilson named the region Big Bear Valley, and the lake he called Lake Big Bear.