A native of Newburgh, New York, Wool entered the army at the outbreak of the War of 1812, and fought with credit at the battles of Queenstown and Plattsburg. He emerged from the war with the rank of colonel and the office of inspector-general. An orphan with little formal education, Wool remained in the service, where he had the opportunity to visit Europe to observe foreign military organizations and operations. He participated in the deportation of the Cherokees from Georgia and Tennessee, and in 1826 was promoted to brigadier general.
The Mexican War gave General Wool another opportunity to distinguish himself. After leading his troops 900 miles from San Antonio, he joined General Zachary Taylor at the Battle of Buena Vista, where his gallant leadership earned him a Congressional sword, a vote of thanks, and the brevet of major general.
In the early days of the Civil War, Wool's quick and decisive moves secured Fort Monroe, Virginia for the Union. The fort guarded the entrance to Chesapeake Bay and the James River, overlooking Hampton Roads and the Gosport Navy Yard, which the Confederates had seized. It was to serve as the principal supply depot of General George B. McClellan's Peninsular Campaign. In May 1862, Wool's troops occupied the navy yard, Norfolk, and the surrounding towns after the Confederates abandoned them; he was then promoted to the full rank of major general. General Wool was reassigned to command the Middle Department, then the VIII Corps. In January 1863, he again assumed command of the Department of the East, and led military operations in New York City during and after the draft riots the next July. Shortly thereafter, General Wool retired from the army following more than fifty years of service. He lived in Troy, New York for the remaining five years of his life.