The community's name means "white lake" in the Salishan dialect of the San Poil tribe,[3] likely a reference to Camille Lake located about 1.25 miles (2 km) north.

Historically, Impach has been the site of traditional Native American dance ceremonies by members of the confederated tribes.

[6] During the early 1930s, a predecessor of the Works Progress Administration established a small logging operation in Impach, which brought some unemployed families to the area at the height of the Great Depression.

A United States post office operated at Impach, Washington, from 1922 to 1954.

Impach is located at the mouth of a long coulee in rural Seylor Valley approximately 3 miles (5 km) west of Inchelium on County Highway 2, also known as Bridge Creek Road.