In 2010 and 2011 EDAC contracted with the New Mexico Office of the State Engineer to georectify several hundred historic water related maps. The first project was to georectify hydrographic survey maps of the Pecos Basin using the 2005 statewide digital aerial imagery as the mapping base. Some of the maps dated as far back as the 1920s. Following the completion of that project EDAC moved to the western side of the state to do a second map georectification project in the Gila / San Francisco Basin. These maps are called Proof of Beneficial Use (PBU) maps and are used in validating historical water use within the state. These maps were especially difficult to georectify because there was almost no control point information on the maps except for the PLSS section and quarter section corners. Because of that we were unable to use a photo map base as was done in the Pecos Basin project. The best mapping base that could be found was the statewide PLSS shapefile and the digital raster graphic (DRG) mosaic of the USGS 1:24,000 map sheets.