Sarah Allen was born on 20 May 1782. Her birth is recorded in the vital records of Avon, Maine, but her parents are not named, and it is not certain that she was born there. She may have been a daughter of Perkins Allen, who with her father-in-law, Capt. Joshua Soule, was one of the founders in 1781 of the unincorporated area known as Township 2 Abbott's Purchase in Lincoln County, Massachusetts, which in 1802 was incorporated as the town of Avon.
Sarah Allen married Joshua Soule at Avon, Maine (then in Massachusetts), on 18 Sep 1803.