100th meridian west
The meridian 100° west of the Prime Meridian of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole. The 100th meridian west forms a great circle with the 80th meridian east.
In the United States, this meridian roughly marks the boundary between the semi-arid climate in the west and the humid continental and humid subtropical climates in the east, and as such roughly connotes the regions of the Eastern and the Western United States.
From Pole to Pole
Starting at the North Pole and heading south to the South Pole, the 100th meridian west passes through:United States
In the United States the meridian 100° west of Greenwich forms the eastern border of the Texas panhandle with Oklahoma. 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 between the semi-arid climate to the west and the humid continental and humid subtropical 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.