William Hays was born on May 9, 1819, in Richmond, Virginia, but at the time of his appointment to West Point in 1836 by Andrew Jackson, he was a resident of Nashville, Tennessee. Hays was graduated in 1840, his classmates numbering W. T. Sherman, George H. Thomas, and Confederate Richard S. Ewell. In the years before the Mexican War, Hays served as a lieutenant of artillery at various points in the northeast; then at the battles of Contreras, Churubusco, and Chapultepec, he won the brevets of captain and major. Except for some duty against the Seminoles, his career until the outbreak of the Civil War lapsed into routine garrison duty. After service in the Washington defenses during the winter of 1861, Hays commanded a brigade of horse artillery in the Peninsular campaign and the reserve artillery of the army at Sharpsburg and Fredericksburg, with promotion to brigadier general of volunteers on December 27, 1862. He directed a brigade of William H. French's division of the II Corps at Chancellorsville, where early in the morning of May 3 he was captured, along with all but one member of his staff, by William D. Pender's brigade of the Confederate Second Corps. However, by May 15 he was delivered at Fort Monroe. There is no record of his subsequent service until the third day of the battle of Gettysburg, when George G. Meade, after the wounding of Winfield S. Hancock and John Gibbon, assigned Hays to command the II Corps, which he directed until September 13. From November, 1863, until February, 1865, Hays acted as provost marshal of the southern district of New York, after which he was assigned to command the 2nd Division of the II Corps, taking part in the siege of Petersburg and the pursuit of the Army of Northern Virginia. Three days before Appomattox, General A. A. Humphreys, who was commanding the corps, found everyone asleep at Hays's headquarters at 6:30 A.M. and relieved Hays with one of his brigade commanders. This unfortunate incident seemingly cost Hays the brevets of major general in the regular and volunteer services. Moreover, his regular rank of major, 5th Artillery, to which he had been advanced in 1863, was never further augmented and was his rank when he died at Fort Independence, Boston Harbor, February 7, 1875. First buried in Yonkers, New York, Hays's remains were moved to West Point in 1894.
Reference: Generals in Blue. Lives of the Union Commanders by Ezra J. Warner. Louisiana State University Press. Baton Rouge.