The river was named for Jacques La Ramie, a fur trapper who visited the area in the early 19th century.

[1] The river rises in northern Colorado, in the Roosevelt National Forest in the Front Range, in western Larimer County.

It flows north-northwest into Wyoming, along the east side of the Medicine Bow Mountains, past Jelm and Woods Landing, then northeast emerging from the mountains 22 miles (35 km) southwest of Laramie.

It joins the North Platte opposite the town Fort Laramie.

The tunnel, which is approximately 2 miles (3 km) long, was finished in 1911 as part of a larger irrigation project for northern Colorado.