100th meridian west

Starting at the North Pole and heading south to the South Pole, the 100th meridian west passes through:

Co-ordinates	Country, territory or sea	Notes
90°0′N 100°0′W	Arctic Ocean
80°6′N 100°0′W	Canada	Nunavut — Meighen Island
79°52′N 100°0′W	Peary Channel
78°44′N 100°0′W	Canada	Nunavut — Ellef Ringnes Island
77°48′N 100°0′W	Unnamed waterbody
76°45′N 100°0′W	Canada	Nunavut — Berkeley Islands and Bathurst Island
74°59′N 100°0′W	Parry Channel
73°57′N 100°0′W	Canada	Nunavut — Prince of Wales Island
71°52′N 100°0′W	M'Clintock Channel
70°35′N 100°0′W	Larsen Sound	Passing just east of Gateshead Island, Nunavut,  Canada (at 70°35′N 100°9′W)
69°58′N 100°0′W	Victoria Strait
69°3′N 100°0′W	Canada	Nunavut — Royal Geographical Society Islands
68°57′N 100°0′W	Queen Maud Gulf	Passing just east of Hat Island, Nunavut,  Canada (at 68°18′N 100°2′W)
67°50′N 100°0′W	Canada	Nunavut Manitoba — from 60°0′N 100°0′W, passing just west of Brandon
49°0′N 100°0′W	United States	North Dakota South Dakota — from 45°56′N 100°0′W Nebraska — from 43°0′N 100°0′W Kansas — from 40°0′N 100°0′W Oklahoma — from 37°0′N 100°0′W Texas / Oklahoma border — from 36°30′N 100°0′W Texas — from 34°34′N 100°0′W
28°0′N 100°0′W	Mexico	Coahuila Nuevo León — from 27°37′N 100°0′W Tamaulipas — from 23°24′N 100°0′W San Luis Potosí — from 23°10′N 100°0′W Tamaulipas — from 22°54′N 100°0′W San Luis Potosí — from 22°50′N 100°0′W Guanajuato — from 21°30′N 100°0′W Querétaro — from 21°12′N 100°0′W Mexico State — from 20°6′N 100°0′W Guerrero — from 18°35′N 100°0′W, passing just west of Acapulco
16°54′N 100°0′W	Pacific Ocean
60°0′S 100°0′W	Southern Ocean
71°55′S 100°0′W	Antarctica	Unclaimed territory

Part of the border between Texas and Oklahoma is defined by the 100th meridian west.

Directors of the Union Pacific Railroad gather on the 100th meridian, which later became Cozad, Nebraska, about 250 miles (400 km) west of Omaha in the Nebraska Territory, in October 1866. The train in the background awaits the party of Eastern capitalists, newspapermen, and other prominent figures invited by the railroad executives.

Sign marking the 100th meridian in Cozad, Nebraska; 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.

In the central Great Plains, the meridian 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. The type of agriculture west of the meridian typically 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.

The song "At the Hundredth Meridian" by The Tragically Hip is about the 100th meridian west, specifically in Canada, and how it has traditionally been considered "where the great plains begin."

• Rain follows the plow