Oscar Littleton Chapman was born in 1896 in Omega, Virginia. Although he attended the University of Denver and the University of New Mexico, he did not earn a degree until 1929, when he received an LL.B. from Denver's Westminster Law School. That same year he was admitted to the Colorado bar and shortly thereafter joined noted Denver lawyer Edward Costigan in private practice. When Costigan ran for the United States Senate in 1930, Chapman handled his campaign, becoming involved in the state's Democratic politics. He served as chairman of the state child welfare committee before serving in 1932 as a delegate to the Democratic National Convention. After running yet another successful Senate campaign, this time for Alva B. Adams, Chapman headed to the White House, where he served under Harold Ickes for thirteen years as assistant secretary of the interior. When Ickes resigned in 1946, President Harry Truman named Chapman to be the acting secretary, but only until Julius Krug was confirmed as secretary later that year. After Krug resigned in 1949, President Truman named Chapman to the position, where he served until the end of the Truman administration in 1953. After leaving the Interior, Chapman remained in Washington, D.C., cofounding a law firm and practicing for the next two decades. Oscar Littleton Chapman died in 1978.