The Northern Pacific Railway purchased this line from Summit, Washington, to Montesano shortly after the PS&GH started operations.

BNSF Railway and Union Pacific Railroad locomotive power are considered home on the PSAP as they run through on these unit trains to Grays Harbor, Washington for unloading.

The Elma Subdivision is the primary mainline for the Puget Sound and Pacific Railroad and is approximately 70 miles in length.

This subdivision handles traffic to and from the Port of Grays Harbor including grain, autos, soda ash, soybean, garbage, manifest, and local trains.

The garbage is loaded into container cars and is shipped via rail to Waste Management's Columbia Ridge Landfill in Arlington, Oregon.