The hardest, most difficult and challenging cycling climbs in and near Yellowstone National Park are, in order of difficulty, %TOP 5.
Old Faithful Geyser
Yellowstone National Park encompasses 2,219,791 acres (8th largest NP) and was the first of the US national parks (established in 1872 by President Ulysses S. Grant). Yellowstone was the 5th most visited national park in 2018 (4,115,000). The park was designated UNESCO World AHeritage Site #28 in 1978 with the following description:
The vast natural forest of Yellowstone National Park covers nearly 9,000 km2 ; 96% of the park lies in Wyoming, 3% in Montana and 1% in Idaho. Yellowstone contains half of all the world's known geothermal features, with more than 10,000 examples. It also has the world's largest concentration of geysers (more than 300 geyers, or two thirds of all those on the planet). Established in 1872, Yellowstone is equally known for its wildlife, such as grizzly bears, wolves, bison and wapitis. More
Dunraven Pass is the biggest climb in Yellowstone NP
Cycling Yellowstone National Park’s Grand Loop - Ride 136 miles gaining 9,615’ passing some of the greatest scenery in the world and most of the Park’s tourist attractions.
We guarantee you will see bison (buffalo) on this loop . . .
Grand loop: The Grand Loop is actually a figure “8” that forms the interior roads of YNP. We did not do the traditional loop, rather we cycled the entire perimeter as we did not have enough time to photo/video the loop and include the extra 22 miles or so to take on the figure 8 route. We began our trek at Roosevelt Lodge at the Northeastern section of YNP. The 141 mile route is on “Grand Loop Road (which is also a number of highways strung together along the perimeter).
At mile 18 you can turn right onto Norris Canyon Road and do 2 Half Loops (Upper Loop - 68 miles and 5,501’ of climbing http://ridewithgps.com/routes/10088756 and Lower Loop - 96 miles and 5,237’ of climbing - http://ridewithgps.com/routes/10088767 ) or continue south on Grand Loop Road for the Full Loop (our term, not YNP’s).
Canyon Village - Mile 18.
The only confusion we encountered was at Old Faithful (mile 68 of on our route). It was not obvious to us what to do at this junction. We strongly recommend turning right into the Old Faithful area and travelling the one mile to the visitor area for lunch.
Visit Old Faithful!
We pass over the Continental Divide at Craig’s Pass at mile 61. It is always a unique and rewarding experience to pass over the Continental Divide (a few of the Top 100 U.S. Climbs do this - e.g. Cottonwood Pass, Wolf Creek Pass and Trail Ridge in Colorado pass over this unique landmark and it is not the average cyclist that ever has this unique experience.
The route has many incredible views and experiences: For example Old Faithful, Yellowstone Lake, following several rivers/streams, geysers, colorful travertine terraces, beautiful rock formations, wild animals (bison for sure and the occasional elk and bear), gorgeous valleys and meadows, rugged mountain ranges and just plain wide open spaces.
The Knock: Traffic, traffic and . . . . more traffic. If you are traffic-sensitive, the full loop is likely not the ride for you. However, we are fairly callous to heavy traffic and were able to focus on our gorgeous surroundings and to a great degree block out the frequent motorhomes and often heavy vehicle traffic.
We recommend going mid-week in the off season and leaving at the crack of dawn.
Leaving Roosevelt Lodge area (we stayed in the cheapo cabins) at sunrise.
YELLOWSTONE NP AND NEARBY CLIMBS
Climbs in the area (beginning at Roosevelt Lodge Cabins, 1 Grand Loop Road, YNP; northeastern YNP):
Cycling Dunraven Pass
Ride 12.8 miles gaining 2,828’ at 3.9%
The main climb in Yellowstone is Dunraven Pass from Roosevelt Lodge.
Cycling Beartooth Pass North
Ride 30 miles gaining 5,743’ at 3.3%
Cycling Beartooth Pass North
Ride 21.5 miles gaining 4,329’ at 3.6%
Ride 13.3 miles gaining 3,070’ at 4.2%
Ride 7.5 miles gaining 2,072’ at 5.2%
Ride 13.2 miles gaining 4,855’ at 6.7%
Ride 17.7 miles gaining 4,756’ at 5%
In clockwise direction beginning at Roosevelt Lodge at the northeast corner of Grand Loop:
 What we did, and what we suggest, is to turn right (if you are doing the loop clockwise) at the signs for Old Faithful, travel the mile to the Old Faithful area which has lodges, a store, deli and Old Faithful.