Forgottonia (/ˈfɔːrɡɒˌtoʊniə/), also spelled Forgotonia, is the name given to a 16-county region in Western Illinois in the late 1960s and early 1970s. This geographic region forms the distinctive western bulge of Illinois (area west of 90° Longitude West) that is roughly equivalent to "The Tract", the Illinois portion of the Military Tract of 1812, along and west of the Fourth Principal Meridian (see Principal meridian). Since this wedge-shaped region lies between the Illinois and Mississippi rivers, it has historically been isolated (river bridge access) from the eastern portion of Central Illinois.