A 1.21-ha plot was established in a mature pine–hardwood forest (Hyatt's Woods) along a low stream terrace in southeastern Arkansas. Compositionally, this stand had considerable arboreal richness, with 26 different tree species ≥9 cm in diameter. Loblolly pine (Pinus taeda) contributed 42% of the stand's 37.1 m²/ha of basal area; the remaining fraction included baldcypress (Taxodium distichum) and 24 hardwood species (no other single taxon exceeded 12%). Only a limited volume (15.2 m³/ha) of dead wood was encountered. The large size of the dominant conifers and abundance of high wood density hardwoods at Hyatt's Woods yielded a considerable quantity of biomass—at 317 Mg/ha, few stands in the region have more. With all species combined, tree stem location exhibited a random spatial pattern, but this changed when individual species were considered. For example, loblolly pine tended to be clustered on the higher portions of this relatively flat site, while white oak (Quercus alba) was well distributed across Hyatt's Woods, and baldcypress was associated with two abandoned stream channels. Unmanaged streamside forests in southeastern Arkansas usually contain high levels of arboreal diversity and biomass, and sometimes possess biological legacies that can date back centuries. These stands retain important structural and ecosystem service components in an otherwise increasingly fragmented and intensively managed landscape.