An economic slowdown after World War I led to a population decrease in the Skykomish Valley, causing Sultan voters to approve a reduction in the city's size in June 1920. The area was home to various illicit industries during the Prohibition era and experienced several major crimes, including the murder of town marshal Percy Brewster on March 2, 1927, by a serial robber who later escaped from prison before being re-captured. The area also experienced an economic downturn during the Great Depression and was home to a Civilian Conservation Corps camp that primarily dealt with firefighting and forest management. The Works Progress Administration also completed several projects in the city, including two expansions of the high school and its gymnasium in 1929 and 1939. Several major fires struck Sultan in the 1940s, including one in October 1945 that destroyed a block of buildings on Main Street and another in 1947 that decimated the Sultan Union High School.