This research aims to identify the processes that influence the structure of eastern redcedar (Juniperus virginiana L.) stands across a range of size classes and in stands that are co-dominated by deciduous species. The trend of eastern redcedar encroachment into prairies and old fields in North America is well-documented; but the mechanisms that shape the distribution of con- and heterospecific trees within stands are poorly understood. Eastern redcedar stands representing a variety of size classes were sampled in the Midwest to examine how stand-shaping processes vary with stand age. Additionally, mature eastern redcedar stands where Quercus spp. are codominant were sampled to evaluate how competitive interactions influence stand structure. Point-pattern analyses were conducted to detect signals of underlying point-processes. We found several signals of density-dependent growth including evidence of self-thinning and regular-spacing between mature individuals. We found segregation within and between mature eastern redcedar and Quercus spp., indicating competitive partitioning of space. These findings indicate density-dependent intra- and interspecific competition are the most important process influencing the structure of eastern redcedar stands in its encroaching range.