Justifying the maintenance of small natural areas requires understanding their contribution to the conservation of specific natural resources. Mount Rushmore National Memorial (MORU) is a small portion of the Black Hills of western South Dakota and eastern Wyoming. Because it has been protected from logging since the late 1930s, it may serve as an important part of the Black Hills forest as a whole. To understand this role, we investigated the extent and degree of logging activities in the memorial and compared the current structure of the MORU forest to that in the rest of the Black Hills today and before Euro-American settlement. Our results suggest that approximately 29% of the park has had no tree harvesting activity, 18% of the park has had only selective cutting of trees, and 66% (344 ha) of the park's area is covered by old-growth forest. Based on current estimates of similar forest in the remainder of the Black Hills, the forest at MORU constitutes the second-largest area of old-growth ponderosa pine forest in the Black Hills. Although the current structure of the forest does not appear to be outside the range of natural variability for this ecosystem, some components of the forest are near the edge of this range. Conservation of this important natural resource will most likely require more active management than has occurred in the past, but this management will require careful consideration because of the rarity of this resource in the region.