is a suburban city about 24 miles south/southwest of downtown Chicago in Bremen Township in Cook County, Illinois, United States. The population was 28,051 at the 2000 census.
The area currently known as Oak Forest was originally called '''Cooper's Grove''' in the early 19th century. Cooper's Grove was then bounded by Kenton, Cicero, Kilpatrick, Lamon, Lavergne and LeClaire Avenues. Mr. Cooper who settled here in the 1830s was said to have been the first resident of Bremen Township. A log cabin discovered by later settlers is believed to have been built by Cooper and was the first home built in the township.
The community was further established when settlers arrived to farm in the area (many of them were German-born), sometime in the mid to late 1840s. The Cooper's Grove post office began service in 1848 and later changed its name to New Bremen alongside the Bachelor's Grove post office which began service in 1843 and later changed its name to Bremen after township governments were established in Cook County in 1850. Neighboring community Tinley Park was part of the community known as New Bremen starting in 1854 until it was later incorporated as Tinley Park in 1892. The population of Bachelor's Grove began to dwindle as people moved to New Bremen/Tinley Park or Blue Island to be along the railroad tracks for more economic opportunities. Christian Goesel settled along 147th and Oak Park Avenue (then Bachelor's Grove Road) in 1861 in a community named Goeselville where a satellite of the New Bremen/Tinley Park post office operated from 1884 to 1903. At its highest peak there were about 30 residents in this area with a few general stores to supply the farmers. This area was absorbed by Oak Forest with earlier settlements now abandoned and forgotten.
The earliest reference to the community as "Oak Forest" (probably so named for its proximity to nearby forest preserves and mature oak trees throughout and surrounding the area) is in an 1893 Chicago, Rock Island and Pacific Railway timetable. Oak Forest was incorporated as a village in 1947, and then incorporated as the City of Oak Forest in 1971. It became a Home Rule Community in 1981. The first Oak Fest Celebration -- now an eagerly anticipated annual event --was first held in 1987.