Born Henry Clay Ross, he never liked the name "Henry" and always used "Harry"; the latter is the name on his marriage certificate and gravestone. Harry Clay Ross was born and raised in Lewistown, Pennsylvania on February 1, 1848. He went to public school and when very young, he became a clerk in a general store. In 1864 (at age 16), he enlisted in Company H, 195th Regiment, Pennsylvania Volunteers, and re-enlisted in Company M, 7th Regiment, Pennsylvania Cavalry, in which he served until the close of the Civil War. He was discharged in Nashville, Tennessee, in June 1865. For several years he was engaged as a clerk at Lewistown, and later he learned the tailoring business, at which he worked in Harrisburg from 1874 to 1878 (ages 26 to 30), after which he engaged in business for himself (working as a "merchant tailor"). His tailor shop was very close to the State Capitol and became a favorite gathering place for Pennsylvania's politicians, who carried on many discussions there and in which Harry Ross played a part.