Sears Woods and Carmean Woods form a 63 ha complex of old-growth, mostly primary forest in the till plains of north-central Ohio. Mesic uplands of the complex are dominated by Acer saccharum and Fagus grandifolia, with Quercus alba, Q. borealis, and Fraxinus americana also common in the canopy. The sapling size class is strongly dominated by Acer saccharum; Quercus and Fraxinus spp. are essentially absent from the sapling size class. This part of the complex corresponds well to descriptions of pre-settlement beech-sugar maple (F. grandifolia–A. saccharum) forest, though the substrate and topography suggest wet beech (F. grandifolia) or beech-oak-red maple (F. grandifolia-Quercus spp.-A. rubrum) forest should have occupied this site. The canopy of the lower, poorly-drained portions of the preserve is dominated by Acer saccharum, Tilia americana, Ulmus americana, and Acer saccharum; the sapling size class was dominated by A. saccharum and U. americana. With the exception of the relatively-high abundance of A. saccharum, the bottomland areas correspond well to early descriptions of the red oak-basswood (Quercus borealis–Tilia americana) phase of the elm-ash (Ulmus–Fraxinus) swamp forest. A Markov Chain model based on most-probable-replacers of current canopy trees predicts a strong increase in A. saccharum and F. grandifolia importance, with a corresponding decrease in Quercus and Fraxinus spp. abundance in the future. The predicted increase in A. saccharum is consistent with the pattern of replacement in 23 recent treefall gaps in the complex. We suggest that changes in regional drainage altered the hydrological regime in such a way as to permit A. saccharum to establish in areas historically too poorly drained for it. In addition, we suggest that the current disturbance regime, which is dominated by small patch size disturbances, fosters the growth of A. saccharum saplings, but not Quercus saplings, into canopy size classes.