The fourth principal meridian, set in 1815,[1] is the principal meridian for land surveys in northwestern Illinois and west-central Illinois,[2] and its 1831[3] extension is the principal meridian for land surveys in Wisconsin and northeastern Minnesota.[1][2] It is part of the Public Land Survey System that covers most of the United States.
The fourth principal meridian begins at a point on the west bank of the Illinois River in Schuyler County, Illinois. The fourth principal meridian's baseline, sometimes called the Beardstown baseline,[citation needed] runs west from this initial point.[1][2] The meridian and this baseline governs surveys in Illinois that are west of both the Illinois River and the third principal meridian.[2]
The Illinois Department of Transportation 2003 Survey Manual gives the point as 40°0′50″N 90°27′11″W / 40.01389°N 90.45306°W and notes that the meridian is an extension of the line north from the mouth of the Illinois River near Grafton, Illinois.[1]
- ^ a b c d "Chapter Five: Land Surveying". Survey Manual (PDF). Springfield, Illinois: Illinois Department of Transportation, Bureau of Design and Environment. 2003-02-28. p. 5. Archived from the original (PDF) on 2011-05-25. Retrieved 2008-10-30.
- ^ a b c d Raymond, William Galt (1914). Plane Surveying for Use in the Classroom and Field (via Google Books) (2nd ed.). New York: American Book Company. p. 456.
- ^ "Part 5: Public Land Survey System". National Mapping Program Technical Instructions: Standards for USGS and USDA Forest Service Single Edition Quadrangle Maps (PDF) (Draft for Implementation ed.). March 2003. pp. 5A-2–5A-4. Retrieved 2008-10-31.