The eastern portion features a combination of gently rolling hills and flat farmland.
The portion between the Illinois and Mississippi Rivers features significantly more hilly terrain, marked with steep valleys.
The largest city of this region is Springfield with a population of 116,250 (2013).
Other Major cities include Galesburg, Peoria and Quincy.
Counties
Adams County
Brown County
Calhoun County
Cass County
Christian County
Fulton County
Greene County
Hancock County
Henderson County
Jersey County
Knox County
Logan County
Macoupin County
Marshall County
Mason County
McDonough County
Menard County
Montgomery County
Morgan County
Peoria County
Pike County
Sangamon County
Schuyler County
Scott County
Stark County
Tazewell County
Warren County
Woodford County