Complex sentence: Elisha William Keyes (January 23,1828-xxxxxx) was a postmaster and mayor in Madison, Wisconsin who rose to the stature of "boss" of the state's Republican party following the Civil War.
Split into simpler sentences: Elisha William Keyes (January 23,1828-xxxxxx) was the postmaster of Madison, Wisconsin, and later was elected its mayor. He rose in stature to become "boss" of the state's Republican party following the Civil War.