Jackson County is the county located to the southeast of Monroe County. It is one of Indiana's largest counties by area and contains a wide variety of terrain. The East Fork of the White River flows through the county from northeast to southwest; the northwestern half of the county is very hilly, while the southeastern half is much flatter. Part of the Hoosier National Forest, including some of the Deam Wilderness, is found in far northwestern Jackson County, which borders a small portion of Polk Township in Monroe County.
The county seat for Jackson County is the town of Brownstown. A very small community southwest of Brownstown, called Vallonia, is the oldest settlement in the region; it was founded by Frenchmen during the 18th century.