Cross-sections of 36 post oaks (Quercus stellata Wang.) were examined to determine the fire history of a post oak woodland in Hamilton County, Illinois. The 226-year tree ring record contained three distinct periods; a fire era from 1776 to1850 having a mean fire return interval of 1.97 years, a fire-free period from 1851 to1884, and a second fire era from 1885 to 1996 having a mean fire return interval of 1.44 years. The fire-free interval corresponds with the rapid settlement of Hamilton County during 1850–85. The fires between 1770 and 1850 are considered landscape fires associated with Native Americans and/or early European settlers, while those between 1885 and 1996 are thought to be due to burning of local woodlands, a practice that became increasingly less common in the late 20th century. Three post oak cohorts were identified, including 211–224 year-old (217-year mean), 137–151 year-old (144-year mean), and 104–115 year-old (105-year mean) age classes. Post oak recruitment ended and fire sensitive hickories (Carya ovata and C. tomentosa), black cherry (Prunus serotina), sassafras (Sassafras albidum), and black oak (Quercus velutina) now dominate the seedling and sapling layers of the woodland.