During World War I, aircraft first served for observation and later for ground support and bombing, making airplane production vital after the United States entered the war in 1917. Early airplanes used linen stretched over wood frames, and Sitka spruce became the preferred wood because it was light, flexible, and strong. Although Sitka spruce grew in the Pacific Coast fog belt from Northern California to Kodiak, Alaska, only Oregon and Washington supplied trees large and plentiful enough for aero-lumber production. In the 1900s, the average spruce tree there exceeded 4 feet in diameter and 160 feet in height. Within the first six months of the war, the Spruce Production Division was organized under Brig. Gen. B. P. Disque to increase lumber production. He recruited 27,661 enlisted men and 1,222 officers from the U.S. Army, and after brief muster at Ft. Vancouver, Washington, these spruce soldiers joined civilians in logging camps and sawmills run by private companies. In 1918, the Sitka Spruce Company operated a sawmill at this site with soldiers of the 103rd Spruce Squadron. Fifty-two enlisted men and two officers lived in a two-story barracks on the grounds and worked around the clock to fill a government order for 1,000,000 board-feet of aero-lumber. The war ended on November 11, 1918, and the Spruce Production Division quickly disbanded, but in less than two years the spruce soldiers had increased lumber production by 300 percent, with nearly 10,000,000 board-feet leaving the Pacific Northwest each month.