Primary old-growth forests are rare in the state of Indiana and are found only in small, isolated patches of nature preserves. Recent research underscores the values of large tracts of secondary old-growth (referred to in this paper as “older” forests), including carbon sequestration, forest resiliency, mitigation of climate change impacts, and conservation of biological diversity. Due to historical management, many portions of Indiana state forests are maturing, and yet the “older” successional stage is underrepresented. One of these maturing forests, the site of our study, is in south-central Indiana within the Back Country Area (BCA) of the Morgan-Monroe/Yellowwood State Forest (two state forests, herein called a complex, including parcels in three counties with the largest block of forests spanning Brown and Monroe counties). Our study of the forest structure of the BCA addresses the following questions: (a) Is this mature forest developing ecological attributes of old-growth forests, thus making it a good candidate for an older forest reserve? (b) Does this forest support the plant community characteristic of natural areas of Indiana? We analyzed forest stand metrics, coarse woody debris and snags, age of the largest live trees, and the floristic quality of the herbaceous layer. We then compared these data with published accounts from Indiana nature preserves. Metrics such as tree basal area, number of large-diameter trees, and number of snags are within the range of those measured in existing old-growth forests of Indiana. Analysis of tree cores and log cross-sections shows that 78% of the sample trees were over 100 yr old, with 24% over 130 yr, which is also comparable to old-growth forest nature preserves in the state. The metrics of the Floristic Quality Assessment of the broader plant community of the BCA are comparable to or higher than the metrics from published assessments of Indiana nature preserves. Collectively, the attributes measured indicate that the BCA supports a maturing secondary forest with old-growth characteristics. In the absence of further timber harvest, the BCA as a reserve could reach older forest status within 50 yr. Our study demonstrates that the BCA forest is a prime candidate for an older forest reserve. This study of the BCA could also serve as a model for future assessments of potential older forest reserves in other state forests. Reserves of older forests free from harvest are not incompatible with other management goals and can be a valuable part of a broader-scale management plan. These forest reserves should be promoted across the state to increase the representation within Indiana's state forest system of late-successional secondary forest exhibiting ecological attributes of old-growth forests, thereby enhancing the role of state forests in biodiversity protection and climate mitigation.