Born in Peru, NY, Pratt designed a milling machine for the George S. Lincoln company of Hartford, Connecticut which became the Lincoln miller, the most important American machine tool of the late 1800s, with 150,000 sold.
With Amos Whitney he organized Pratt & Whitney in 1860 to manufacture machine tools, tools for the makers of sewing machines, and gun making machinery for use by the Union Army during the American Civil War. He is credited with being first to permit production of fine gear work. Pratt promoted interchangeable parts and the adoption of a standard system for gages for the United States and Europe. Among several machine-tool patents, his most important was for planing metal granted on July 28, 1869.
He died in 1902 Hartford, Connecticut.