Third Principal Meridian Initial Point, Illinois

The establishment of the Third Principal Meridian followed Indiana’s Second Principal Meridian and Ohio’s First Principal Meridian. It was surveyed in 1815, to measure the land that would soon become the State of Illinois. The meridian originates from a Point of Beginning at the intersection of a baseline in the southern part of the state. The original marker is now under the surface of Highway 51. A monument was installed next to the road in 1976 to commemorate the Initial Point, but also to serve as an officially surveyed offset point (known as a witness corner), since the original location is in the middle of a highway now. This is one of 37 federal survey points of origin covering the USA (outside of the 13 original colonies), known as Initial Points, selected over a span of 150 years, to anchor newly acquired federal land to the legal and cartographic grid.