Harrison was admitted to the New York State Bar in 1905. He was admitted to the New Jersey state bar as an attorney in 1904, and in 1907 he was admitted as a counselor. He then became a member of the law firm Munn & Church in Newark.
A Republican, he was a member of the Republican County Committee of Essex County for several years. He was elected to the Caldwell Borough Council in 1905 and served as mayor starting in 1908. By 1913, he was a director of the Caldwell National Bank and the Essex National Bank of Montclair.[1]
In 1911, Harrison was county counsel of Essex County. He was prosecutor of pleas for Essex County from 1917 to 1922. He was counsel of the Essex County Bar Park Commission and a member of the State Board of Bar Examiners.
He was named receiver for the Breeze Corporations, Inc. He was also a director of the Firemen's Insurance Company of Newark and the National State Bank of Newark.[3] He was president of the New Jersey State Bar Association in 1931.[4]