Land surface and subsurface states (e.g., soil moisture) are critical for analyses of land-atmospheric interactions in climate studies. It is expected that the variation in soil moisture across the Southern Great Plains (SGP) domain will affect these interactions. In support of continuing soil moisture research applications on a mesoscale level at the SGP, the Oklahoma Mesonet Soil Moisture (OKMSOIL) value-added product (VAP) is now in production. A joint project between Oklahoma State University and the University of Oklahoma created more than 100 surface mesonet stations in Oklahoma in the early 1990s, hereafter referred to as the Oklahoma Mesonet (OKM). The dense surface network of OKM provides a good representation of land surface/subsurface conditions over the region. However, the OKM product alone does not provide the information necessary to calculate soil moisture across the network. OKMSOIL provides 30-minute-averaged products for the soil matric potential (capillary force needed for the soil matrix to hold water), volumetric water content (total percent of water per volume of soil), and fractional water index (relative measure of soil wetness) at all OKM surface stations, including those near the SGP Central Facility.