In this paper, a ribcage FE model of the 50 percentile male composed of all quadrilateral and hexahedral elements were developed using an interactive multi-block hex meshing approach. The block-building and meshing techniques for reducing the model development effort and time were presented by the use of the anatomical symmetry and multiple block edition tools. Furthermore, regional variations in cortical bone thickness along the parameter and longitudinal directions of the rib structure were assigned to each of the ribs by mapping the actual cortical thickness distribution of the ribs measured in the published data. The ribcage FE model was then validated against experimental data under the hierarchical structure level from rib segment, rib ring and to full ribcage. Overall, the FE model predictions were reasonably within the range of the force-displacement corridors in experiments. This study represents a major effort in the development and validation of the thorax model for the Global Human Body Modeling Consortium. The combined hex meshing and cortical thickness mapping techniques presented here would be useful for the development of anatomically-detailed FE models to understand the biomechanics of human thorax and other human body structures.