He was born in Butler County, Ohio, of Dutch and Irish descent. During his infancy his parents removed to Fountain County, Indiana, near Veedersburg. He graduated at Indiana Asbury University (now DePauw University), Greencastle, Indiana, in 1849; was admitted to the bar in 1850, and began to practice in Covington, Indiana, whence in 1857 he removed to Terre Haute.

In 1858-60 he was U.S. district-attorney for Indiana; in 1861-66 and in 1869-73 he was a Democratic representative in Congress; and in 1877-97 he was a member of the U.S. Senate. During the American Civil War he seems to have been affiliated with the Knights of the Golden Circle, but he was not so radical as Clement Vallandigham and others.

He was a member of the Finance Committee throughout his service in the Senate, and his first speech in that body was a defence of the free coinage of silver and a plea for the preservation of the full legal tender value of greenback currency, though in 1893 he voted to repeal the silver purchase clause of the Sherman Act. He had an active part in bringing about the building of the new Congressional Library. He was widely known as an effective advocate, especially in jury trials. In allusion to his unusual stature he was called "the Tall Sycamore of the Wabash." He died in Washington, D.C., in April 1897.

Some of his speeches were published under the title, Forty Years of Oratory (2 vols., Indianapolis, Indiana, 1898), edited by his three sons and his daughter, Harriet C. Voorhees, and with a biographical sketch by T. B. Long.