Comparisons of current and historical tree species composition and size structure along natural productivity gradients are useful for inferring effects of disturbance regimes and productivity on patterns of succession. We tabulated occurrences and estimated diameters of 3483 General Land Office bearing trees across 19 survey townships along an upland soil texture and organic matter gradient in north Mississippi. We then contrasted this presettlement composition and structure with that of 2998 trees in sampling plots within present-day mature (>100 years old) upland forests contained within the survey townships. Presettlement upland communities appeared to consist of non-successional communities, in which the most abundant trees were shade-intolerant, fire-tolerant trees (e.g., Quercus marilandica [blackjack oak]) in both large and small size classes across the entire soil gradient. These fire-prone pre-settlement assemblages differed greatly from present-day mature uplands, which were transitional assemblages of upland and floodplain trees, with mesophytic floodplain species (both early and late-successional) dominating the smaller size classes.