Once the Mississippi was opened following the fall of Vicksburg and Port Hudson, naval activity on the river virtually ceased. In this period of relative calm, USS "Baron De Kalb" (ex-"St. Louis") was sunk in the Yazoo River by two Confederate torpedoes on July 13, 1863. Much of the Mississippi Squadron, including the five remaining City-class gunboats, took part in the ill-fated Red River campaign, in which they were almost lost because of falling water levels. This was their final significant action.