OK, I am just gonna paste the description verbatim from the
Adventure Cycling website. We are using their maps and routing anyway, so here is the DL according to the wise sages at AC...
Photo by Aaron Teasdale
Ride the longest off-pavement route in the world.
The Great Divide Mountain Bike Route (GDMBR) is Adventure Cycling's premier off-pavement cycling route, crisscrossing the Continental Divide north to south. This route is defined by the word "remote." Its remoteness equates with spectacular terrain and scenery. The entire route is basically dirt-road and mountain-pass riding every day. In total, it has over 200,000 feet of elevation gain.
The route is geographically divided into five regions. The diverse nature of the regions makes for an incredible visual, sometimes spiritual experience. The route offers something different every day — whether it be riding conditions, scenery, points of interest, or folks along the way. It is a route to be enjoyed for its diversity.
A wide variety of road conditions exists along this route. Surfaces range from pavement, good gravel roads, four-wheel-drive roads, singletrack, or old railroad beds. There is an excellent opportunity to view wildlife such as bear, deer, wild horses, pronghorn antelope, eagles, osprey, sandhill cranes, and other birds and animals. The route is rich in history, with ghost towns, deserted mines, wagon routes, and old Spanish land grants. The route is near or goes through several national parks such as Glacier, Yellowstone, and Grand Teton. Temperatures tend to be chilly at night and cool to warm in the days as you are in mountainous regions most of the way. Wind really isn't a factor along the route because you spend a lot of time in the cover of trees, with the exception of the Great Basin area. Snow, hail, and afternoon thundershowers can be a factor. Getting up and riding early to avoid the afternoon thundershowers is advisable. Medical help is often a long distance off of the route, so riding within your abilities and being aware of dangers is a must. Mosquitoes are a fact of life — take repellant.
Beginning at the Canadian border and heading south to Helena, Montana, you are in the deep woods and steep mountains near Glacier National Park and the Bob Marshall Wilderness. This area is native to grizzly bear, elk, moose, mountain lion, thick woods, and has some difficult climbing. Montana is characterized by mountainous riding in tall forests with occasional dips into small towns. It is also noted for its friendly people. The capital city in Montana, Helena, has less than 40,000 people and a nice small-town feel to it. The other big town along the route is Butte, which has a definite blue-collar, mining flavor. Montana also has the toughest downhill on the route — nicknamed "thermarest hill" for all the thermarests it has eaten. Even the hardiest riders have to walk this one.
From Butte to Pinedale, Wyoming, you'll be riding through wide-open mountain valleys. The vegetation thins out into valleys with many different varieties of sage and high-elevation alpine woods. The route crosses the Continental Divide many times, and the climbing is longer with very steep sections on some of the roads. You'll see many cows. You leave Montana crossing the divide into Idaho. You are only in Idaho for 72 miles and ride along some blue-ribbon fishing streams and an old railroad bed on the west side of Yellowstone National Park. You'll cross into Wyoming between Yellowstone and Grand Teton National parks on a very scenic road with some great backcountry campsites and a genuine undeveloped hot springs. The route cuts through a corner of the Tetons before heading east up over the divide again and then down the west side of the Wind River Range. The prettiest alpine region on the whole route can be found here. Just south of Pinedale, is a stretch with the worst mosquitos on the entire route but makes for a great character builder. Farther on there's the unforgetable sensation of riding on the crest of the divide for several miles. You then hit an extremely picturesque section of high desert following the Lander cutoff — part of one of the westward wagon routes. Water is very scarce through here, so carry plenty. After dropping into the twin ghost towns of South Pass and Atlantic City, you will cross the Great Basin — a place of almost no drinkable water and no trees. Big northwest winds blow across vast open territory marked with wild horses and antelope. Rawlins, Wyoming, marks the end of the desert.
From southern Wyoming to northern New Mexico, you'll be in the Colorado Rockies. The ascents on the route stretch out to long mountainous climbs at elevations starting at 8,000 feet or above. Incredible aspen stands, huge mountains, beautiful alpine meadow flora, historical tourist towns, and a less remote wilderness setting are the characteristics of this state. Expect early evening thunderstorms and cold nighttime temperatures. The highest pass of the route is Indiana Pass, elevation 11,910 feet, in southern Colorado. Soon after crossing it, you get to see firsthand what kind of scars mining can leave on the land as you pass right through a federal Superfund site. Heading into New Mexico, the road surface deteriorates, with much more rocky riding. Here the countryside turns much drier, and water sources can be few and far between. Climbs get shorter and steeper. Geographically this region is as remote as any place in the continental United States. Mesas, cliff lines, volcanic formations, and mountain ranges that seem to pop right out of the desert floor are major visual features of this area. Many different cactus and grass varieties somehow provide habitat for small rodents, snakes, and lizards. Townspeople are right out of Old Mexico, with Spanish spoken more than English. Late-summer monsoon rains turn roads into sloppy, red clay and can fill many of the dry creek beds on the route in seconds. Roads are impassable until they dry out. This area is both historically and anthropologically dominated by the rich Native American and southwestern Spanish culture. Coming down the east side of the Gila Wilderness is a welcome relief, with water once again available as you head into Silver City, New Mexico, a place noted for learning about Anasazi culture with the Gila Cliff Dwellings National Monument north of town and a good museum at the local university. From there it is a sprint south (mostly on pavement) to the border crossing, which consists of one building on the border and nothing else for miles and miles.
