other regiments to form the 3rd Infantry. This is why the 3rd Infantry is the oldest Infantry unit in the active United States Army rather than the 1st Infantry. 1815 to 1861 As of 30 November 1819, the regiment was located on the northwestern frontier at Fort Howard in Green Bay, Wisconsin. As of 9 November 1822, the regiment had 6 companies in Green Bay, two in Sarnac and two in Chicago. The annual report of the Army from 1826 showed that the regiment had been re-located to Jefferson Barracks, Missouri. As of November 1837, the regiment's headquarters and six companies were at Fort Jesup in Louisiana with the other four companies at Fort Towson in Oklahoma. From 1840 to 1843, the 3rd Infantry fought in the Seminole War in Florida. During the Mexican War, the regiment fought in most of the major battles of the war including Palo Alto, Monterey, the invasion and Siege of Vera Cruz, Cerro Gordo, Churubusco and Chapultepec which led to the capture and occupation of Mexico City. From 1856 to 1860, the regiment served in New Mexico where it fought the Navajo Indian tribe. After serving in New Mexico, the regiment was spread out to various posts on the Gulf of Mexico from Florida to Texas. American Civil War The 3rd Infantry saw extensive service during the United States Civil War and was credited with 12 campaigns. Detachments from the regiment were serving at Fort Pickens in Florida and in Saluria on the Gulf Coast of Texas when the war began in April 1861. Three companies of the 3rd Infantry surrendered on 25 April. Five of the regiment's 10 companies were engaged at the Battle of Bull Run on 20 July 1861. The regiment spent most of the war assigned to the Army of the Potomac and served mostly in Virginia. From May 1862 to March 1864, it served with 1st Brigade, 2nd Division of the 5th Corps. In March 1864, it was reassigned to the 4th Brigade, 1st Division of the 5th Corps. It participated in the Siege of Yorktown (part of the Peninsular Campaign), the Battle of Malvern Hill, the Second Battle of Bull Run, the Battle of Antietam, the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, the Battle of Cold Harbor and the Battle of Appomattox. 1865 to 1917 After the Civil War, the 3d Infantry served