John Ellis Wool was born 29 February 1784 in Newburgh, New York. At an early age, both his parents passed away; thereupon he was removed to Troy to live with his grandfather, James Wool. His formal education was limited to that of a country school, and at the age of twelve he entered the store of a Troy merchant and remained with him for six years. During the next decade he worked at various places including the law office of John Russell. When the War of 1812 broke out, he raised and headed a company of volunteers in Troy, and on 14 April 1812, he was commissioned a captain in the 13th Infantry. His troops were engaged in action at the battles of Queenstown and Plattsburgh. In between the battles he was promoted to a major in the 29th Infantry on 13 April 1813, and, afterwards, was brevetted a lieutenant colonel on 11 September 1814. He was made colonel and inspector general of the Army on 29 April 1816 and maintained this grade for more than a quarter of a century. As inspector general, Wool's duties required visits to military posts to ascertain the fighting effectiveness and preparedness of the troops.

In 1836 Wool was ordered to Cherokee country in Georgia, Tennessee, and the Carolinas to assist General Winfield Scott in transferring the native peoples to Oklahoma in accordance with the terms of a treaty of 1835. It would prove to be a difficult mission as Wool's conduct was called into question by Alabama civil authorities for allegedly seizing private property for subsistence and other provision needed by soldiers and Cherokees. As a result, Wool was recalled from service, but was later exonerated by a court of inquiry. Shortly thereafter, Wool was ordered to command troops along the United States-Canada border in northern New York and New England to ensure American neutrality during the Canadian Rebellion. Problems arose from many Canadian refugees and sympathetic Americans who had designs on annexing Canada. They were engaged in cross border raids and other subversive activities that nearly instigated a conflict with Great Britain. The forces under the command of Wool and others were successful in quelling such activities and thus preserving peace.

The Mexican War of 1846-1848 provided Wool with an opportunity for active and distinguished service. Now a brigadier general, Wool virtually mobilized, trained, and marched his own army, composed mostly of western volunteers, for the invasion of Mexico by land. Placed under the command of General Zachery Taylor as commander-in-chief with Wool second in command, this army won the Battle of Buena Vista in 1847. Wool was commended for his achievement and presented with decorative awards of honor by the United States Congress, State of New York, and Troy, in subsequent years.

Then followed the quieter years of peace, which were actually a troubled brief interlude between the Mexican War and the Civil War, then already brewing. Wool served as a commander at the Department of the East most of these years allowing him to maintain headquarters in Troy. In 1854, Wool was transferred to the Department of Pacific, headquartered in San Francisco, California with orders from President Pierce to halt filibustering expeditions against Mexico. In the course of duty, Wool placed under arrest the French Consul, Dillon, who was tried for complicity in such activities by a San Francisco jury. This action provoked anger from the French government, which subsequently led the Pierce administration to abandon support of Wool's course in literally carrying out the President's orders. Shortly thereafter, his headquarters were transferred to a bleak part of Benicia, where he would have to contend with the problem of land disputes between white settlers and native people in the Oregon and Washington territories. Having limited manpower and supplies for such a large expanse of territory, Wool's solution was to exclude settlements west of the Cascade Mountains. This action resulted in a bitter dispute with the Oregon and Washington territorial governors, George L. Carry and Isaac Stevens, respectively, who already felt Wool was not responding quickly enough to protect white settlers. Ultimately, Wool was again relieved of command for political reasons.

The Civil War provided Wool one last opportunity for military service. He was seventy-seven years old, and in seniority and rank, he was second only to General Winfield Scott, whose career also dated back to the War of 1812. Despite his advanced age, Wool performed duties of remarkable variety and intensity. As commander of the Department of the East, first from Troy, with its nearby Watervliet Arsenal, and then from New York headquarters, Wool mobilized the resources of the most populous region for military service. Then, later in 1861, he was moved closer to the front to command the Department of Virginia, with headquarters at Fortress Monroe. There he extended the Union line by the capture of Norfolk, and was quite critical of General George McClellan for his dilatory program in preparing his forces for the capture of Richmond.

General Wool's final tour of duty was in 1863, as military commander of New York City, so important politically and economically for the conduct of the war. Here, he lived through the draft riots, which nearly tore the city apart. He shared with the police and State militia responsibility for suppressing the riots.

Instead of support and commendation for his effort, Wool was retired from active duty on 1 August 1863, and he returned to Troy, where he stayed for the remainder of the war. Despite his seventy-nine years, he was never fully reconciled to retirement perhaps as much for the manner as the fact of what he regarded as a peremptory dismissal.

From his home in Troy, almost to his death on 10 November 1869, General Wool continued to write long letters to the War Department and General Grant demanding a kind of exoneration, if not reinstatement. On his death, he received a ceremonial funeral befitting a war hero in his hometown. He was survived by his wife Sarah Moulton whom he married 27 September 1810. They had no children. She passed away five years later. He was buried with high military and civic honors in Oakwood Cemetery at Troy. During the year 1879, a high monolith was raised to his memory.