The Mcintosh formation was named and described by Snavely, Ran, Hoover, and Roberts (1951) from beds that are well exposed in road cuts along State Route 5H on the south side of Mcintosh Lake.

naming of

State Route 5H was later renamed to State Route 507
A lot of time has passed since this report was published. Today there does not seem to be very obvious roadcuts on the south side of McIntosh Lake based on street view maps. There are some spots that may be the exposed formation (hard to tell), e.g., here.

Washington State Route 507 (Wikipedia) State Route 507 (SR 507) is a Washington state highway in Lewis, Thurston and Pierce counties that extends 43.52 miles (70.04 km) from Interstate 5 (I-5) and U.S. Route 12 (US 12) in Centralia to SR 7 in Spanaway. The highway also intersects SR 510 in Yelm and SR 702 in McKenna. The first appearance of the roadway on a map was in 1916 and since, two highways, Secondary State Highway 5H (SSH 5H) and SSH 1N, were established on the current route of SR 507 in 1937 and 1943. They both became SR 507 during the 1964 highway renumbering.

Geology and coal resources of the Centralia-Chehalis district, Washington (pubs.usgs.gov) The Centralia-Chehalis coal district includes about 570 square miles in south western Thurston County and northwestern Lewis County, Wash., midway between Seattle, Wash., and Portland, Oreg., and forms a part of the subbituminous and lignite coal fields of southwestern Washington. It adjoins the Morton coal field on the east and the Toledo coal field on the south. It includes a part of the extreme western foothills of the Cascade Range and a part of the eastern border of the Coast Ranges.