The only US-Mexican American War (1840s) battlefield in the US is in southern Texas just outside the modern town of Brownsville. The battle took place in the vicinity of a resaca (oxbow pond) and the movement of troops and their artillery pieces was strongly influenced by the presence of wetlands. The area is now preserved as Palo Alto Battlefield National Historical Park, and managed by the National Park Service, but has been used for agriculture, particular cotton growing for more than a century and the native vegetation has been altered. A goal of the Historical Site is to restore the hydrologic regime and vegetation of the battlefield back to the condition, as near as possible, of what was present in the 1840s. We are working with NPS staff to develop restoration options for resacas and the wet prairies (dominated by Spartina spartinae). Water originated historically with summer floods from the Rio Grande, which now is highly regulated, rarely floods, and is lined with high dikes to restrict floodwater to the channel. In addition, periodic hurricanes drenches the area with large precipitation events that can also produce local flooding since the areas is flat and contains clay soils. Our current project is to determine the hydrologic processes occurring in the area, and to determine whether natural areas and the former agricultural lands are wetlands. We are exploring these concepts with ground and surface water investigations and also by measuring soil redox potential to determine if the soils have reducing conditions for long duration during the year.