"Neosho", named after the Neosho River that flowed through Kansas and Oklahoma, and the first of her name, was laid down in mid-1862 by James Eads at his Union Iron Works in Carondelet, Missouri. She was launched on 18 February 1863 and commissioned at Cairo, Illinois on 13 May 1863, with Commander John C. Febiger in command, but was not completed until 1 July. She left Cairo on 14 July 1863 and reached Vicksburg on 6 August, just over a month after it had surrendered after a lengthy siege. "Neosho" and other warships patrolled the Mississippi and its tributaries to prevent Confederate raiders and flying batteries from ambushing Union supply ships. One example was on 8 December 1863 when "a Confederate shore battery attacked and disabled the merchant steamer "Henry Von Phul"; "Neosho" and steamed up to defend the ship and silenced the battery."