James T. McElvany was the oldest son of John Sidney McElvany and Sara Elizabeth Lowe McElvany. Before the outbreak of the Civil War, he was a school teacher. When the war broke out, he joined Company F (Gwinnett County, GA), 35th Regiment, Georgia (Volunteer) Infantry, Confederate States Army as 1st Lieutenant on Sep 23, 1861. He was elected Captain on May 9, 1862. Capt McElvany was wounded at the Battle of Cedar Run/Mountain, in Culpeper County, Virginia, on Aug 9, 1862. His regiment was attached to the Army of Northern Virginia and he fought at the Battle of Gettysburg where he kept a diary of the events (he was a prolific writer and also wrote poetry). Elected Major (Field & Staff Company) on May 19, 1864. On sick furlough Feb 28, 1865 through the end of the war. He served as sheriff of Gwinnett Co. from 1868-70, and Justice of the Peace in 1877. He was elected to the Georgia House of Representatives in 1882, serving 3 years.

The 35th Georgia Infantry Regiment was organized at Atlanta, Georgia and mustered into Confederate service at Richmond, Virginia in October, 1861. The men were recruited in the counties of Troup, Haralson, Bartow, Walton, Chattooga, Harris, and Gwinnett. The regiment was first assigned to General French's Brigade and in April, 1862, had a force of 545 effectives. Later the regiment served under Generals Pettigrew, J.R. Anderson, and E.L. Thomas, Army of Northern Virginia and fought in numerous battles from Seven Pines to Cold Harbor, during the long Petersburg siege south of the James River, and was surrendered at Appomattox with 15 officers and 121 men. The regiment sustained 70 casualties at Second Manassas, 89 at Fredericksburg, and 33 at Chancellorsville. Of the 331 engaged at Gettysburg, more than twenty-five percent were killed or wounded. The field officers were Colonels Bolling H. Holt and Edward L. Thomas; Lieutenant Colonels Gustavus A. Bull, W.H. McCullons and Edward L. Thomas; and Majors William L. Groves, J.T. McElvany, and Lee A. J. Williams.