Bear Lake is a natural freshwater lake on the Utah-Idaho border in the Western United States. It is the second largest natural freshwater lake in Utah and has been called the "Caribbean of the Rockies" for its unique turquoise-blue color, the result of suspended limestone deposits in the water. Its water properties have led to the evolution of several unique species that live naturally only within the lake. It is supposed that Bear Lake was formed at least 150,000 years ago by fault subsidence that continues today, slowly deepening the lake along the eastern side.
Originally named Black Bear Lake by Donald Mackenzie, an explorer for the North West Fur Company who discovered the lake in 1819, the name was later changed to the current Bear Lake. The lake is a popular destination for tourists and sportsmen and the surrounding valley has gained a reputation for having high quality raspberries
According to folklore, Bear Lake holds a lake monster: the so-called Bear Lake Monster. Although this originated with Joseph C. Rich, who later admitted to making up the monster, people continue to report sightings of the monster today.
Although the lake lies relatively near the Oregon Trail, which runs north and east of the lake, and was traveled by many pioneers between 1836 and the 1850s, it seems none of them went south enough to view the lake. It wasn't until 1863 that Mormon pioneers led by Charles C. Rich settled in the Bear Lake Valley, but they made an agreement with Native Americans which left most of the Utah portion of the valley in Indian possession. The Mormons gradually moved south and established the villages of Garden City, Pickleville, and Laketown, each along the lake's shore.
In later years Bear Lake became a resort and recreation area, and this tradition has grown through the years with many developers selling lakeshore and mountain view lots. The beaches of Lakota and Ideal were given to private development in the 1970s, including the Blue Water and Sweetwater developments. The State of Utah bought the far southeast beach for use as a State Park, and also operates a marina on the lake's west side.
Environmental concerns have arisen with the ongoing development of the area. The lake is diked on the Idaho side and downstream Bear River water users use it as a reservoir.
The lake and surrounding areas are a popular summer tourist destination. The lake has many marinas, beaches, and two tourist towns in Utah known as Garden City and Laketown. It also has two state parks, each named Bear Lake State Park: one in Idaho, one in Utah.
Bear Lake has a high rate of endemism (species living naturally only in one place). Several species evolved in the lake's waters, but after the diversion of the Bear River into the lake, many of these have gone extinct. Remaining known endemic species of fish include the Bonneville cisco, Bonneville whitefish, Bear Lake whitefish, and Bear Lake sculpin. Although other species have been introduced into the lake, few can reproduce successfully in the lakes waters, so it has not been affected as greatly as other lakes by invasive species.
Water from the lake is used for irrigation in the nearby Bear Valley in southeast Idaho, and for recreational fishing. The lake drains via the Bear River Outlet, completed in 1915 into the Bear River which eventually flows into the northeast portion of Great Salt Lake.
The climate in the valley is warm and dry during the summer, with first snowfall coming during the fall. Fog and snow are common during the winter. The lake is icebound during most winters and most of spring during freeze years.
Many locals from northern Utah, southern Idaho, and western Wyoming come to Bear Lake for summer vacations due to its proximity and abundance of recreational activities.