5 states · Glacier NP to the Mexican border · about 3,100 miles of trail · Pacific vs Atlantic drainage
Continental Divide map
The Continental Divide is the line along the Rocky Mountain crest that separates rivers flowing to the Pacific from rivers flowing to the Atlantic and the Gulf of Mexico. In the US it crosses Montana, Idaho, Wyoming, Colorado and New Mexico.
Where the divide is
The Great Divide enters the US from Canada at Glacier National Park in Montana. It runs south along the Lewis Range, swings west to the Idaho border, follows the Bitterroot and Beaverhead crests as the Idaho–Montana line for about 300 miles, then turns east through Yellowstone into Wyoming. It crosses the Wind River Range, splits around the Great Divide Basin, enters Colorado at the Park Range, winds through Rocky Mountain National Park and the Sawatch and San Juan ranges, and leaves New Mexico for Mexico at the state's southwestern bootheel. Every other state is entirely on one side or the other.
Which way the water goes
- West of the divide: the Columbia and Snake (to the Pacific), the Colorado (to the Gulf of California), and the closed Great Basin of Nevada and Utah, whose rivers never reach any sea.
- East of the divide: the Missouri, Platte, Arkansas and Rio Grande, all to the Gulf of Mexico by way of the Mississippi or directly.
- Triple Divide Peak in Glacier National Park, 8,020 ft, sends water three ways: to the Pacific, to the Gulf of Mexico and, through the Saskatchewan system, to Hudson Bay.
- The Great Divide Basin in Wyoming, about 3,900 square miles around Interstate 80, drains to neither ocean; the divide runs around it on both sides.
Passes across the divide
| Pass | State | Elevation (ft) | Route |
|---|---|---|---|
| Marias Pass | Montana | 5,213 | US 2 and the BNSF railway, south edge of Glacier NP |
| MacDonald Pass | Montana | 6,312 | US 12 west of Helena |
| Homestake Pass | Montana | 6,329 | Interstate 90 at Butte |
| Monida Pass | Idaho–Montana | 6,823 | Interstate 15 |
| Togwotee Pass | Wyoming | 9,658 | US 26/287 east of Jackson Hole |
| South Pass | Wyoming | 7,412 | The Oregon, California and Mormon trails |
| Loveland Pass | Colorado | 11,990 | US 6; the Eisenhower Tunnel (Interstate 70) passes beneath the divide nearby |
| Monarch Pass | Colorado | 11,312 | US 50 |
| Wolf Creek Pass | Colorado | 10,857 | US 160 |
Cities on or near the divide
Butte, Montana, sits within a few miles of the divide, and Helena is just east of it. Leadville, Colorado, the highest incorporated city in the US at about 10,150 ft, is on the east side beneath Mount Elbert. Denver is 50 miles east of the crest; Grand Junction lies on the west side. Silver City and Grants in New Mexico are the closest towns on the southern section. In Wyoming the divide passes within sight of Interstate 80 at Rawlins.
How the divide shaped the map
The Idaho–Montana border follows the divide from the Canadian line to the Yellowstone area, one of the few places where a state boundary follows a watershed. Every early expedition was organised around it: Lewis and Clark crossed at Lemhi Pass in 1805, and the Oregon Trail used South Pass because it was the only gentle crossing. The Continental Divide Trail runs about 3,100 miles along or near the crest from Mexico to Canada. Politically, the western water compacts of the 20th century (the Colorado River Compact, the Columbia treaties) are drawn along the same line.