This Civil War feature is the only earthwork remaining of the eleven constructed by the Confederates to guard the Orange and Alexandria Railroad at Manassas Junction (now the city of Manassas). Put up by enslaved laborers and local troops under Col. George H. Terrett, the Mayfield Fortification was begun in May 1861 and completed the following month. Confederate soldiers occupied the earthwork until March 1862 and Union troops held it from August 1862 to November 1864. The Mayfield Fortification is listed in the registers under the Civil War Properties, Prince William County Multiple Property Documentation form.  It is one of only two surviving Civil War earthworks in the city of Manassas; Cannon Branch Fort was likely constructed later in the war by the Union army. Now owned by the city, the Mayfield Fortification is expected to yield archaeological data relating to the periods of occupation by Confederates and then Union troops, and its relationship to other, now-vanished, area forts.