It is on the southwest side of the Henrys Lake Mountains of northern Fremont County, approximately two miles south of the continental divide along the Montana state line, just west of Targhee Pass and north of Sawtell Peak.

The lake lies less than ten miles (16 km) across the continental divide from the headwaters of the Missouri River in southwestern Montana.

After receiving word that the Nez Perce had entered the wilderness area, General Oliver O. Howard rested for several days on the side of the lake.

It was later discovered by an Ashton resident that the military did not want to interfere with trumpeter swans which used the lake as a breeding ground.

The western and eastern edges of the lake provide wetland/marsh habitats that serve as breeding areas for many birds in spring.

Notable at Henrys Lake are white pelicans, widgeon, lesser scaup, cormorants, red-necked and western grebes, coots, mallards, bufflehead, ring-necked ducks, Canada geese, blue-winged teal, eared grebe, killdeer, common merganser, common tern, cinnamon teal, trumpeter swans, great blue heron, California seagulls, bald eagles, Swainson's hawks, red-tailed hawks, red-winged blackbirds, cowbirds and more.

[13] Frome Park on the west shore of Henrys Lake is owned and operated by Fremont County.

Many northbound through hikers opt out of this section when leaving Yellowstone National Park and entering the Centennial Mountain Range in Idaho.