Technical Abstract: The objective of this study was to characterize soil organic carbon (SOC) with pyrolysis molecular beam mass spectrometry (py-MBMS) and then to determine correlations between the mass spectra and associated soil characterization data. Both soil carbon chemistry and the organic forms in which SOC is sequestered (soil microbial biomass (SMBC), particulate organic matter carbon (POM C), and mineral associated carbon (Cmin C)) were assessed by multivariate statistical analyses to discover existing correlations and if they could be developed into estimative models. The sample set consisted of well-characterized soils collected from native prairie sites in the western U.S. Corn Belt and Great Plains: eleven sites located within eight mid-western states (CO, NE, IA, ND, MT, TX, MO, and MN). Sample characterization parameters included site, depth, % SOC, POM C, Cmin C, SMBC, and SOC calendar age (determined from 14C age). Estimative correlations were found for samples collected across this large geographic region (at or greater than 0.90) for SOC, POM C, Cmin C, and SMBC. SOC calendar age derived from radiocarbon-14 dating could be estimated for ustollic soils from MT, NE, and CO. These soils also contained deeper and younger aeolian layers, whose ages were correctly estimated with this technique. Py-MBMS analysis additionally showed that soils developed from water-sorted sediments on a tilled-floor lake plain (lacustrine soils) were significantly different from the other samples.