Spine degeneration can lower injury tolerance and influence injury outcomes in vehicle crashes. To date, limited information exists on the effect of age and sex on thoracic spine 3-dimensional geometry. The purpose of this study is to quantify thoracic spinal column and canal geometry using selected geometrical measurement from a large sample of CT scans. More than 33,488 scans were obtained from the International Center for Automotive Medicine database at the University of Michigan under Institutional Review Board approval (HUM00041441). The sample consisted of CT scans obtained from 31,537 adult and 1,951 pediatric patients between the ages of 0 to 99 years old. Each scan was processed semi-automatically using custom algorithms written in MATLAB (The Math Works, Natick, MA). Five geometrical measurements were collected including: 1) maximum spinal curvature depth (D), 2) T1-to-T12 vertical height (H), 3) Kyphosis Index (KI), 4) kyphosis angle, and 5) spinal canal radius. The data were analyzed by sex and age. Maximum spinal curvature depth occurred at T6, irrespective of age and sex. It continuously increased with age. Spinal curvature depth was generally larger in females than males in particular in children and in the 75+ age group. Results from this research are among the first to quantify the effect of diverse factors, such as age and sex, on detailed thoracic spine anatomy using a large and continuous sample of pediatric and adult CT scans. The results can be used to help understand the occurrence of severe injury in low severity crashes.