[1] Pinney attended Racine College in Wisconsin, General Russell's Collegiate and Commercial Institute in New Haven, Connecticut, a common school in Helena, Montana, an academy in Iowa, and the University of California.
He spent the two years working as a Tutor in St. Mark's School in Southborough, Massachusetts, and DeVeaux College in New York.
[2] After graduating, Pinney moved to New York City, New York, where he worked for the law firm Evarts, Southmayd & Choate and its successor Evarts, Choate & Beaman, where he worked until 1886.
[3] Pinney resided in New Brighton, Staten Island since 1888, and was an active member of the local Republican Party.
In 1895, he was elected town supervisor of Castleton and District Attorney of Richmond County.
During World War I, he was a member of the police reserves, head of the local draft board, chairman of the Legal Aid Society that cared for the insurance of soldiers, and frequently spoke on behalf of Liberty Loan drives.