Under Townsend's command the "Essex" participated in the Siege of Port Hudson which occurred from May 21 to July 9, 1863, when Union Army troops assaulted and then captured the Mississippi River town of Port Hudson, Louisiana. Along with the Mortar Flotilla, the "Essex" bombarded the area daily and helped bring about the surrender of the city. The Union's success in this battle gave Northern forces effective control of the Mississippi River and effectively cut the states of Arkansas and Texas off from the rest of the confederacy.