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Eastern South Dakota (SD) is a mosaic of grasslands, wetlands, and cultivated agriculture. A continued shift from grassland to cropland has occurred over the past 10 years and is expected to continue for the next 50 years. Land conversion will influence cumulative erosion from arable soils which will negatively impact ecosystem goods and services and agricultural production. Quantifying historical erosion rates and coupling these with trends in land management will aid in the development of land use models capable of estimating landscape scale externalities such as soil loss, water availability, flow regimes and quality. At present, the National Agricultural Statistics Survey can only produce reliable approximations of soil erosion at a state level from 1982 forward. This leaves a gap in knowledge of erosion prior to 1982. This is partially due to missing spatial and temporal land cover data for SD. However, an alternative source (thematic map) has recently been made available by the United States Geological Service of the contiguous U.S. from 1938 to 1992 which categorizes land cover for each year. These data may be used to generate missing erosion data prior to 1982 in order to better calibrate models estimating landscape scale externalities. Newly published land cover maps will be used to expand soil erosion data before 1982 to better understand the historic and future impacts of diminishing grasslands and land management choices. Erosion data generated using the thematic land cover map will be regressed against values generated from the NRCS erosion data for the period 1982-1992 for validation. Preliminary results will generate estimations of erosion from 1982 to 1992 using the RUSLE2 and make approximations possible for 1938 to 1981 erosion in SD. Additional erosion data will allow for a better understanding of land use and management decisions coupled with expected declines in grasslands.