Thomas Salvester Allen was born in Centerville, New York, on May 25, 1837. His parents were Timothy and Elizabeth (Hess) Allen.
When Thomas was age 15 the family moved to White Water, Wisconsin. In 1861, he enlisted in the Union Army and served in the 13th Wisconsin Infantry. He was a private. The gun that he carried during his service is still in the possession of one of his descendants.
Thomas married Mary Adell Rogers on July 4, 1856, in Jefferson County, Wisconsin.