The Coal Trail follows the right-of-way of the Northern Pacific Railroad branch line developed in 1886 to export coal from the Roslyn Cle Elum Coal Field. The Roslyn Branch was extended in 1887 to the #3 Mine site where the community of Ronald developed. The branch line intersected the Northern Pacific Railway's Cascade Line in Cle Elum and for decades constituted the primary transporation link between the Upper Kittitas County communities of Cle Elum, Roslyn and Ronald.

The Roslyn Cle Elum Coal Field measures 21 square miles and produced millions of tons of high quality coal during the late 19th and early 20th centuries. Peak production came in the 1920s when 1.8 million tons per year were mined and exported for industrial and domestic uses. The last local coal extraction enterprise, #9 mine, closed operations in December 1963.

The Roslyn Ronald branch remained operational until 1986 for delivery of coal imported from Utah to the Roslyn Fuel Company in Ronald. The Roslyn Foundry also continued to receive rail shipments of coke fuel for its cupola furnace that produced iron castings. In 1987, the Roslyn/Ronald branch line was decommisioned and the tracks and ties were removed from the right-of-way.

In 1994, the governments of the City of Roslyn, City of Cle Elum, and Kittitas County adopted an Interlocal Agreement that established the Coal Mines Trail Commission to convert the branch line right-of-way to a public recreational trail and underground utilities corridor.