Frank Rosebrook Millspaugh was born on April 12, 1848 in Nichols (town), New York. He was an alumnus of Shattuck School, now Shattuck-Saint Mary's, Faribault, Minnesota.
A protégé of James Lloyd Breck, he was made deacon on June 22, 1873 by Henry Benjamin Whipple, and ordained to the priesthood by the same bishop on June 21, 1874. Millspaugh was dean of Trinity Cathedral (Omaha, Nebraska) from 1876-1886, when he became rector of St. Paul's Church, Minneapolis, Minnesota.
He was consecrated Bishop of Kansas on September 19, 1895.
He died on November 22, 1916.