In 1949, a series of soil samples were taken from selected fields at the Riesel Texas watershed research station. The samples were dried and stored in a dry location for over 50 years. The sample labels were accurate enough for the field locations to be identified even after 50 years had passed. In 2004, we sampled these fields again to compare soil properties. This report deals with the soil organic carbon content comparisons of the archived and modern soil samples and the results of a agricultural model simulating actual management practices. The modern samples were taken in about the same depth increments as the archived samples. The effect of management was determined by measuring organic carbon content of soil samples archived in 1949 and samples obtained in 2004 from the same fields and soil depths. By 1949, intensive agricultural practices had degraded the Soil Organic Carbon (SOC) content, from about 3.4% in the surface 15 cm of the native grassland (SW-12) to less than 1% in the agricultural fields. Converting to Bermuda Grass increased SOC concentration in the surface 15 cm. Modern agricultural practices, probably improved fertilization, also increased SOC in the surface 15 cm). In addition, the soil carbon content in the surface 90 cm was simulated for several management practices common in central Texas including: a native grassland, small grain and row crop production, and row crop production prior to grass forage and hay production. Accompanying data sets include daily weather and annual management practices between 1949 and 2004. The measured data served as a validation data set for the APEX agricultural simulation model.