Complex sentence: He served as Chief Justice of Pennsylvania (1851--1854), Pennsylvania Supreme Court Justice (1851--1856), Attorney General (1857--1860) and the U.S. Secretary of State (1860--1861) under President James Buchanan.
Split into simpler sentences: He served as a Pennsylvania Supreme Court Justice (1851--1856) and Chief Justice of Pennsylvania (1851--1854). He later served as U.S. Attorney General (1857--1860) and the U.S. Secretary of State (1860--1861) in the administration of President James Buchanan.