The United States declared war on Germany in April 1917. Largely through the efforts of Chillicothe attorney John Poland, the War Department selected Chillicothe as the site of an army training camp for inductees from Ohio, West Virginia, and western Pennsylvania. Construction began at Camp Sherman, named for Civil War general William Tecumseh Sherman, in June 1917. When the first recruits arrived in September, more than fourteen thousand workers had erected two thousand buildings on the 1,700-acre site. The rapid influx of soldiers increased Chillicothe's population from 16,000 to 60,000.
The worldwide Spanish influenza epidemic arrived at Camp Sherman in September 1918. Of the 8.000 people infected, 1,100 died within two months. Two hundred German prisoners were interned here from July 1918 to September 1919. Four divisions — 123,581 men — trained at Camp Sherman. The 83rd and 84th divisions went overseas, but the 95th and 96th did not complete training before the November 1918 armistice. Discharges began within days and were completed by July 1920. The government sold the buildings but retained the land, now the site of two correctional facilities and the Veterans Administration hospital.