He was born in Cummington, Massachusetts. After graduating from Yale University in 1839, he taught for a time at Greenfield, Massachusetts, and also edited The Greenfield Gazette. In 1842 he was admitted to the bar and began the practice of law at North Adams, where for a time he conducted The Transcript. He served in the Massachusetts House of Representatives in 1848-1849 and in 1852, in the state Senate in 1850, and in the Massachusetts constitutional convention iii 1853. From 1853 to 1857 he was United States district attorney for the western district of Massachusetts; and from 1857 to 1875 he was a Republican member of the national House of Representatives. In 1875 he succeeded Charles Sumner as U.S. senator from Massachusetts, serving until 1893. During this long period of legislative activity he served in the House on the committees on elections, ways and means, and appropriations, took a prominent part in the anti-slavery and reconstruction measures during and after the Civil War, in tariff legislation, and in the establishment of a fish commission and the inauguration of daily weather reports. In the Senate he was chairman of the committee on Indian affairs, and gave much attention to the enactment of laws for the benefit of the Indians. On leaving the Senate, in 1893, he became chairman of the Commission to the Five Civilized Tribes (sometimes called the Dawes Commission) and served in this capacity for ten years, negotiating with the tribes for the extinction of the communal title to their land and for the dissolution of the tribal governments, with the object of making the tribes a constituent part of the United States. Dawes died at Pittsfield, Massachusetts in 1903.