Vernon was platted in 1815, and after Jennings County was formed by the Indiana General Assembly in 1817, Vernon became the county seat that same year. The Madison-Indianapolis Railroad reached Vernon in 1839, and the masonry arch that elevated the track over Pike Street remains. Vernon still operates under its amended 1851 incorporation by the General Assembly, which authorized a mayor and local elections in March. In 1976, Vernon was listed as a Historic District in the National Register of Historic Places. Many of its structures were built before 1900, including some dating from the 1820s through the 1840s. A fire on October 13, 1859, destroyed homes and businesses on Pike Street opposite Court House Square. Federal, Greek Revival, Italianate, and composite architectural styles blend there into a historic mosaic.