and
Oklahoma is defined by the 100th meridian west gather on the meridian in the
Nebraska Territory at what is now
Cozad, Nebraska, in 1866 ; photograph taken 138 years after the preceding photograph in October 2004 In the
United States the meridian 100° west of Greenwich forms the eastern border of the
Texas panhandle with
Oklahoma (which traces its origin to the
Adams-Onís Treaty in 1819 which settled the border between
New Spain and the United States between the
Red River and
Arkansas River).
Dodge City, Kansas lies exactly at the intersection of the Arkansas River and the 100th meridian. As first noted by
John Wesley Powell in the 1870s, there is a big difference in rainfall by the different sides of the meridian. In the central
Great Plains, it roughly marks the western boundary of the normal reach of moist air from the
Gulf of Mexico, and the approximate boundary (although some areas do push the boundary slightly farther east) between the
semi-arid climate to the west and the
humid continental (north of about
37°N) and
humid subtropical (south of about
37°N) climates to the east. West of the meridian, raising livestock is much more economically important than east of it, and what
agriculture does exist relies heavily on irrigation. Historically, the meridian has often been taken as a rough boundary between the eastern and western United States. White settlement, spreading westward after the
American Civil War, settled the area around this meridian during the 1870s. A sign across
U.S. Highway 30 in
Cozad, Nebraska, marks the place where the 100th meridian intersects with the routes of the
Oregon Trail,
Pony Express,
transcontinental railroad, and the
Lincoln Highway. ==In popular culture==