The U.S. Army's Spruce Production Division was a major logging and spruce manufacturing operation under the command of General Brice P. Disque, who was appointed to direct the cutting of spruce and other trees for Allied aircraft production. In the Pacific Northwest, The Industrial Workers of the World (IWW) had dramatically slowed logging throughout the region with a series of strikes and slowdowns primarily aimed at forcing employers to improve conditions in the logging camps and to institute an eight-hour day. After consulting with employers, the American Federation of Labor (AFL), and members of the Washington Defense Council, Disque used a mixture of force and concessions to fight the IWW. General Disque dispatched a number of soldiers to work as loggers and to harass IWW organizers. He also convinced the War Department to add an eight-hour day requirement to all of its contracts with logging companies in the region.

In May, 1918, the Siems, Carey-H.S. Kerbaugh Corporation contracted with the U.S. Army to build a camp and establish Spruce Railroad No. 1 to Lake Pleasant, Clallam County, Washington. Seattle architecht Carl Gould was hired to design a site to house and support over 2,000 soldiers and civilians just southwest of the town of Beaver on the shores of Lake Pleasant. The ten-mile long Hoko logging road has its start in Siemscarey. The camp was built between July and November, 1918. On November 11, 1918, the war ended and construction on the camp was halted. On November 30, 1918, the railroad to Siemscarey was completed and was subsequently used to carry materials dismantled from the camp. No timber harvested from this area was used for the war effort.

Between 1918 and 1919, the company town of Siemscarey was home to over 3,000 resident and visiting soldiers and civilian workers. It had its own post office, separate from the one in Beaver, as well as a hospital (temporary tent buildings), women's building (completed), sawmill (temporary, main mill not completed) and mess hall (temporary, main facility not completed). The current town of Beaver, Washington, now encompases the site of Siemscarey. There were two known deaths listed at Siemscarey. The cause of death in each case was attributed to pneumonia.

The following Spruce Army Squadrons were stationed at Siemscarey between 1918 and 1919: 115th beginning in October 1918; 122nd and 123rd from September to November 1918; 124th from September 1918 onwards; 21st Provisional (later 85th Spruce) from September to November 1918; 24th Provisional (later 87th Spruce)from September 1918 onwards; 36th Provisional (later 96th Spruce) from September 1918 onwards.