He remained at the Academy as an instructor until 1829, then had garrison duty and served as a staff officer in operations against the Creek Indians early in 1836 before moving to Washington, D.C., in July as Captain of Ordnance.
Parrott resigned from the army four months later to become the superintendent the West Point Iron and Cannon Foundry on the opposite (east) bank of the Hudson River in Cold Spring, New York, with which he would be associated for the remainder of his life.
While employed at the foundry, Parrott and his brother Peter also assumed management of the operation of the Kemble-owned furnaces in Orange County, New York, on the Hudson's west bank.
The brothers purchased a ⅓ interest in Greenwood Furnace from a minority holder in 1837, and bought it entirely from the Kembles in 1839.
However, he continued to experiment with artillery shells and fuses at West Point until his death at Cold Spring at the age of 73.