After peaking in the late 19th century, the county's population declined during the 20th, in common with much of the rural Midwest. The widespread adoption of the automobile in the 1920s undercut small-town businesses, which were threatened further by the Great Depression of the 1930s. World War II and the economic revival of the late 1940s and 1950s drew people to better jobs in growing regional cities, and this further diminished small towns. The population shrank again in the 1980s due largely to the effects of the "farm crisis" of low crop prices, high farmer debt and other economic causes.