South Middleton Township is approximately 51.6 sq. miles, consists of 111.18 Township road miles, and has a population of approximately 16,000, as of 2020. The Township was established in 1810 when it was divided off from the former Middleton Township. When the area was divided, North and South Middleton Townships were created.
The Township is bordered on the north by Carlisle Borough, North Middleton Township, and Middlesex Township, on the east by Monroe Township and Silver Spring Township, on the west by Dickinson Township and West Pennsboro Township, and on the south by Adams and York Counties. The Township surrounds the Borough of Mount Holly Springs, although the Borough is not a part of the Township. South Middleton is a Township of the Second Class and operates under the provisions of the Pennsylvania Second Class Township Code under a council manager arrangement. The governing body consists of five elected supervisors.
The Township staff includes a Township Manager, Assistant Manager, Administrative staff, Community Development and Planning Department, Road Department, and Parks and Recreation Departments. South Middleton also has an elected Tax Collector and three elected Auditors.