William Norman Cunningham Collection on the Pacific Coast Cement Company, 1914-1958

The Pacific Coast Cement Company was located on a 20-acre site along the East Duwamish waterway near Charleston Street. The plant was designed and built in 1928 by the Pacific Engineering Company of Seattle, under the supervision of Chief Engineer S.E. Hutton. The company began producing its product, Diamond Cement, 10 months after construction started. The cement plant was accessible by highway, railroad and ship along a private 460-foot wharf.

To supply the plant with raw materials, a clay pit was excavated on the west side of the Duwamish waterway. A gas-driven Bucyrus shovel dug shale from the hillside and the material was transported to the factory by truck. A limestone quarry was established on Dall Island, Alaska, about 700 miles from Seattle. Ships could unload 6,000 tons of Alaska limestone at the Seattle plant wharf in 36 hours.

Portland cement is manufactured by first grinding limestone and clay then mixing it with water. This slurry is fired at high temperatures in coal-heated rotary kilns. After firing, the resulting “clinker” is cooled, ground, mixed with gypsum and other materials, then milled to an extremely fine consistency to produce cement. At its peak, the Pacific Coast Cement Company was capable of producing 3,400 barrels a day. Cement is mixed with sand, water and gravel to produce concrete.

While in operation, the Pacific Coast Cement Company used the products and services of four other subsidiaries: Pacific Coast Coal Company Mines, the Pacific Coast Steamship Company, Pacific Coast Railroads and Pacific Coast Engineering. Pacific Coast Cement Company sold its northwest holdings to the General Construction Company in 1947.