THE IMPACT OF VICKSBURG LOESS ON THE 1863 SIEGE OF VICKSBURG, MISSISSIPPI

The City of Vicksburg, Mississippi was besieged by the armies of MG U.S. Grant from 18 May until 4 July 1863--47 days. During this time the civilian and military populations of the city were cut off from the outside world and suffered terrible depredations. Although not realized at the time, the geologic character of Pleistocene Vicksburg Loess both contributed to and alleviated the suffering of the people inside Vicksburg. First, the loess topography, resulting from its erosive nature, provided safe defiladed positions for soldiers and civilians alike, while the dendritic drainage around the city formed almost impregnable positions for Confederate fortifications. Unfortunately, Confederates would soon learn that the effectiveness of these fortifications was greatly dependant upon loess properties--1863 regulations and standards for fortifications notwithstanding. The loess topography also provided the Confederates with good places to observe Union activity, to the detriment of MG Grant’s plans in at least one case. Second, the calcium carbonate structure within the loess allowed the City’s defenders and citizens to construct caves to escape the constant pounding of shell and mortar fire. However, this same property allowed Union besiegers to tunnel completely under the opposing works to set explosive charges. Further, with its internal structure destroyed, the loess quickly became fine dust that caked the soldier’s clothing and equipment and turned roads to quagmires after summer showers. This condition worked hard especially against the Confederates who had no place to go but to their trenches. Third, the geohydrologic properties of loess contributed to the shortage of water within the city during the siege and therefore indirectly to the outbreak of disease and to the inability of the Confederates to tread wounded soldiers. Vicksburg Pleistocene Loess did not cause the surrender of the City of Vicksburg. It is correct to say, however, that the loess properties influenced the events of the Siege of Vicksburg and the way the siege was conducted.