Truman won election as judge of Jackson County, Missouri, in 1922, an administrative rather than judicial position. He won with the backing of local political leader Thomas “Boss Tom” Pendergast. Truman had served in World War I with Pendergast’s nephew James. Truman lost reelection in 1924, but won the position of presiding judge of Jackson County in 1926. He held this position until 1934.