Complex sentence: At the age of 34, Pitchlynn was elected by the council as principal chief in 1860 of the Choctaw Nation of Oklahoma, after most of the Choctaw had been removed to Indian Territory (later Oklahoma).
Split into simpler sentences: At the age of 34, Pitchlynn was elected by the council in 1860 as principal chief of the Choctaw Nation of Oklahoma. By this time, most of the Choctaw had been removed to Indian Territory (later Oklahoma).