The purpose of this study is to characterize the variable microstructure of the elderly human rib in an attempt to elucidate its contributions to biomechanical adaptive responses and fragility. Histological sections were made from Basic Fuchsin stained bilateral 6th ribs from 10 elderly post-mortem human subjects (PMHS). Percent Porosity Area (% Po.Ar), mean Osteon Area (On.Ar), mean Crack Length (Cr.Le), Crack Density (Cr.Dn), and Crack Surface Density (Cr.S.Dn) were successfully quantified and analyzed. ANOVA results indicate that all variables show significant inter-individual variation, but no significant bilateral variation within individuals. Subject variation could contribute to differential individual fragility. Paired t-tests revealed cortex differences for these variables (most are significant) between compressive and tensile cortices in a presumed cyclic bending loading pattern in the rib. These findings can contribute to interpretations about loading history and mechanical adaptation as well as bone behavior prior to failure. A methodological investigation into microfracture data collection showed significant differences between a “total” dataset and a “sampled” dataset. Therefore, it is recommended that only microfracture data collected from the entire rib cortex be utilized in future studies until a more representative sampling method can be developed. This study should prompt investigators to incorporate a histological perspective into interpretations as to why and how bone failure may occur and what contributes to fracture risk in the elderly rib in both modern and past populations.