Major-General John Newton was born in Norfolk, Virginia on 24 August 1823. He was appointed to West Point in 1838 and graduated 2nd in the class of 1842. After graduation, he taught engineering at West point for three years, then devoted himself to the construction of fortifications.

The outbreak of the Civil War found him as chief engineer of the Department of Pennsylvania, and he assisted in preparing the defenses of the national capital.

The rank of brigadier-general of volunteers was bestowed upon him in September 1861, and he remained with the organization which was eventually the First Corps, Army of the Potomac, as brigade and division commander, being made major-general of volunteers in March 1863.

He succeeded to the command of the crops after John Fulton Reynold's death at Gettysburg on 1 July 1863, and led it until it was discontinued on 24 March 1864.

Newton's appointment as major-general of volunteers expired in April 1864, and with his former title, he succeeded Sheridan in a division of the Fourth Corps, Army of the Cumberland. After the war, he continued in the regular army and reached the grade of brigadier general in 1884, being retired in 1886.

Newton's most renowned achievement was the removal of the reefs at Hell Gate in New York harbor. General Newton was commissioner of public works, New York city, from 1887 to 1888 and then president of the Panama Railroad Company.

He died on 1 May 1895. Newton has a marker on the grounds of Gettysburg battlefield that reads: Army of the Potomac, 1st Corps Headquarters, Major General John Newton, July 2 & 3, 1863. He is buried at West Point National Cemetery.