Harrison was an active supporter of the Republican Party's platform and served as Republican State Committee's secretary. After Wallace, his law partner, was elected as county clerk in 1860, Harrison established a new firm with William Fishback that was named Fishback and Harrison. The new partners worked together until Harrison entered the Union Army after the start of the American Civil War. Harrison was born on a farm by the Ohio River and graduated from Miami University in Oxford, Ohio. Harrison was an active supporter of the Republican Party's platform and served as Republican State Committee's secretary. After Wallace, his law partner, was elected as county clerk in 1860, Harrison established a new firm with William Fishback that was named Fishback and Harrison. The new partners worked together until Harrison entered the Union Army after the start of the American Civil War.