Born: February 9, 1819, Danbury, New Hampshire.
Died: September 24, 1904, Wellesley, Massachusetts.
Buried: Hope Cemetery, Worcester, Massachusetts.
William was the son of Jonathan C. Sleeper and Mary Parker, husband of Emily T. Sleeper, and father of William Sleeper.
He attended Phillips-Exeter Academy, Exeter, New Hampshire; the University of Vermont; and the Andover Theological Seminary, Newton Centre, Massachusetts.
After ordination, he conducted home ministry work in Massachusetts and Maine. He later became pastor of the Summer Street Congregational Church, Worcester, Massachusetts, and served there over 30 years.