In 1807, he was commissioned a lieutenant in the State Militia, and eventually became a captain.
He was for three years Town Clerk of Minisink, a Justice of the Peace, and an associate judge of the Orange County Court.
He was a delegate to the New York State Constitutional Convention of 1821.
Hallock was elected as a Jacksonian to the 19th and 20th United States Congresses, holding office from March 4, 1825, to March 3, 1829.
He died on December 6, 1840, and was buried at the Hallock family cemetery near Ridgebury, New York.