USS Essex was built at St. Louis, Missouri in 1856 for use by Wiggins Ferry Company and was originally named New Era. Purchased by the War Department on 20 September 1861, the ferry was converted into a timberclad gunboat by James B. Eads of St. Louis, and assigned to duty with the Western Flotilla, an organization maintained, operated, and controlled by the Army but commanded by a naval officer.
New Era, commanded by W. D. Porter, steamed to Cairo, Illinois and operated on the Ohio and Mississippi rivers in October. She then took part in an expedition up the Cumberland River on 30 October before returning to St. Louis in mid-November for conversion to a partial ironclad. During the conversion, the ship was renamed Essex.
On 7 and 11 January 1862, Essex and St. Louis engaged Confederate gunboats in the Tennessee River near Lucas Bend, Missouri. In company with six other gunboats commanded by Flag Officer Andrew H. Foote, she cooperated with the Army in capturing Fort Henry, Tennessee on 6 February. During this action Essex suffered a penetrating hit that severely damages her boiler, killing 11 and wounding 23 of her crew, including Porter.
Worried about rumours relating to the Confederate ram CSS Arkansas, Essex was extensively modified and repaired, including new, protected boilers, heavier armor and a 45-foot hull section inserted in the middle of the ship. Following the yard work, Essex steamed south and participated in the assault on Vicksburg on 13 July 1862. Nine days later she ran past the hammering batteries of Vicksburg and, in company with Queen of the West, attacked Arkansas, inflicting considerable damage. Since her engines were not strong enough to carry her back north, Essex retired south to Baton Rouge, Louisiana. On 5 August she joined with the Army in repelling a Confederate attack there and the next day Essex attacked Arkansas again; during the engagement, Arkansas broke down and drifted ashore where she was destroyed by her crew.
In September, Essex retired to New Orleans for a refit. During that period, the entire Western Flotilla, including Essex, was turned over to the Navy on 1 October 1862 in compliance with congressional enactment and thereafter was named the Mississippi Squadron.
Essex acted in the capture of Port Hudson, Louisiana from 8 May to 8 July 1863. The daily bombardment of the area by Essex and Mortilla helped bring about the eventual surrender of that city. On 9 July she engaged the enemy at Donaldsonville and although damaged in the battle, carried out her patrol duty at this point through 6 March 1864 when she sailed with the fleet into the mouth of the Red River and assisted in the capture of Fort de Russy on 15 and 16 March. Unfortunately, her draft was too deep to proceed further up river and on 17 April Essex got underway for Vicksburg where she arrived 6 days later.
On 4 May she proceeded to Memphis, Tennessee where she remained as a guardship for the duration of the war. On 27 April 1865, following the massive boiler explosion in steamship Sultana, Essex's boats help rescue 60 people from the water. Essex was decommissioned at Mound City, Ill., on 20 July 1865, and sold on 29 November 1865.
Part of the text is incorporated from the United States Navy's Dictionary of American Naval Fighting Ships, a work in the public domain.