Southern Precinct, formerly township, is Congressional Township 10 South, Range 2 East of the Third Principal Meridian

Third Principal Meridian

The Third Principal Meridian begins at the mouth of the Ohio River and extends north to the northern boundary of the state of Illinois, and with the base line in latitude 38° 28' 20", governs the surveys in the state east of the third principal meridian, with the exception of those projected from...

 located in Williamson County, Illinois

Williamson County, Illinois

-2010:Whereas according to the 2010 U.S. Census Bureau:*92.7% White*3.8% Black*0.4% Native American*0.8% Asian*0.0% Native Hawaiian or Pacific Islander*1.7% Two or more races*0.4% Other races*2.0% Hispanic or Latino -2000:...

. It's name is generic as there have never been any large communities or trade centers within it, though it is home to Pulley's Mill. The most well-known institution that lies within the precinct is the United States Penitentiary, Marion

United States Penitentiary, Marion

The United States Penitentiary is a Federal Bureau of Prisons facility located in Southern Precinct, unincorporated Williamson County, Illinois. The facility is located south of Marion, from St. Louis, and from Chicago. It was built in 1963 to replace the Alcatraz prison in San Francisco, which...

, which lies in the north-central part of the precinct. The Lake of Egypt

Lake of Egypt

Lake of Egypt is a reservoir in the Little Egypt region of the U.S. state of Illinois. It is located six miles south of Marion, Illinois and covers 2,300 acres with of shoreline. The lake has an average depth of with a maximum depth of...

Dam is also located in the Precinct, as is the northwestern part of the lake itself.