Born in Massachusetts, Belknap was a farmer and mechanic by trade, but also attended singing school from the age of 18.
Most of his 85 known compositions were published in tune books. Of particular note is Belknap's devotion to an American musical idiom devoid of influence that comes from European training. His 1797 The Harmonist's Companion demonstrates this unique quality, and many of his compilations are devoted solely to American music.
Belknap's only known instrumental composition, Belknap's March, was published in 1809 in The Middlesex Songster.