Henry S. Eggleston was originally from Georgia, Vermont. Sometime between 1845 and 1849 he married Elizabeth A. Washburn of Belleville, Ontario and they settled in Potsdam, New York. In the summer of 1849 he moved to Wisconsin after a brief stay in Michigan, and Elizabeth joined him shortly thereafter.
After settling in Wisconsin, Eggleston was Postmaster of Appleton, Wisconsin, and established Egglestons Real Estate, Insurance, Loan and Collecting Agency. Based on the content of his letters and postmaster appointment, Eggleston was a staunch Democrat.
In May 1861 he received a captain's commission in the Ripon Guards, Wisconsin Active Militia. By fall this unit had become the Ripon Guards (Company B) of the 1st Regiment of Wisconsin Cavalry. In June 1862 he was promoted to major in the 1st Wisconsin Cavalry.
Henry S. Eggleston died in Milwaukee on December 11, 1862 of diphtheria while returning to his regiment in Missouri.
