The Fossil Trees of Washington State

According to William D. Boehm, king county Washington has coal deposits with:

"Huge numbers of polystrate trees imbedded in 14,200 feet of conformable deposits ... renton, tukwila and raging river formations."

Boehm also provided the following reference: Geology and coal resources of the cumberland, hobart, and maple valley quadrangles, king county, Washington, Geological survey professional paper 624, 1969.