Born in Highland, New York, Pratt attended the public schools and Claverack Academy at Claverack, New York. He engaged in the lumber and coal business. He was also interested in banking. He served as member of the Board of Supervisors of Ulster County 1895-1897. He was a member of the New York State Assembly in 1897. He served as director of the First National Bank of Highland since 1900 and of the Kingston Trust Co. since 1921. He was president of the Board of Education of Highland, New York from 1908 to 1926.
Pratt was elected as a Republican to the Sixty-ninth and to the three succeeding Congresses (March 4, 1925 - March 3, 1933). He was not a candidate for renomination in 1932. He resumed his former business interests. He died from injuries received in an automobile accident near Highland, New York, May 21, 1934. He was interred in Highland Cemetery.