Mortenson Lake National Wildlife Refuge is located in southern Albany County in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

 and includes 1,776 acres (7.2 km²). The refuge is managed by the U.S. Fish and Wildlife Service an agency within the U.S. Department of the Interior. Mortensen Lake NWR is a high altitude refuge and has several small alpine lakes of which Mortenson Lake is the largest. At 7,256 feet (2,211 m) above sea level, the refuge provides protection for numerous migratory bird species.
In 1984, the Wyoming Toad

Wyoming Toad

The Wyoming Toad or Baxter's Toad is an extremely rare amphibian that exists only in captivity and within Mortenson Lake National Wildlife Refuge in the U.S. state of Wyoming. The Wyoming Toad was listed as an endangered species in 1984, and listed as extinct in the wild since 1991...

 was listed as an endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 and was widely believed to be extinct in the wild. A small population of the toad was rediscovered in 1987 in the area surrounding Mortenson Lake which led to the establishment of the refuge in 1993. Since 1995, offspring from captured examples of this extremely rare amphibian

Amphibian

Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

 have been released into the wild to help stabilize the remaining population. The refuge is closed to all public access to aid in recovery efforts of this endangered species.

Mortenson NWR is administered by Arapaho National Wildlife Refuge

Arapaho National Wildlife Refuge

The Arapaho National Wildlife Refuge is a United States National Wildlife Refuge located in north central Colorado. The refuge is located in North Park in central Jackson County south of the town of Walden. The refuge was established in 1967 to furnish waterfowl with a suitable place to nest and...

 in Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

.