Yellowstone National Park, created in 1872 as the world's first national park, comprises 2.2 million acres (3472 square miles), and despite the fact that there are over 370 miles of paved roads, most of Yellowstone is managed as wilderness (less than 3% of the park is roads and facilities), offering 1210 miles of trails and over 300 designated backcountry campsites.
Yellowstone National Park is 80% forest, 15% meadows, and 5% water. Though mostly in Wyoming, small portions are in Montana and Idaho, which is why all three state flags fly high atop Old Faithful Inn.
Here's a view of Shoshone Lake after a hike of 3 miles on DeLacey Trail from Grand Loop Road (Hwy. 89).
My first night's camp was at the southwest corner of Shoshone Lake, with a great view of the lake. Be advised that the circuit around the lake requires a half-dozen or so fordings of creeks and rivers -- no bridges are available and no downed trees are handy for your use, probably because any fallen trees are swept away by spring melt floods.
The scariest was fording Moose Creek on the southern part of the trail, which for me was running with a very strong current and at one point was chest deep, due mainly to the heavy snowfall during the winter of 1996-1997 which was responsible for all the drainages running at higher than normal levels. The fording of Lewis Channel (photo below) was the longest, but it had little current and a very stable small-pebble bottom surface, making it an easy ford.
A nice fringe benefit was hiking through the Shoshone Lake Geyser Basin at the far western end of the lake. It is billed as one of the world's most important basins with over 70 geysers, including 15 foot by 5 foot Minute Man Geyser seen steaming in the background of this photo below. This geyser basin is far less visited than others in Yellowstone due to the long hike necessary to reach it. The trail meanders through the basin with no retaining walls or boardwalks, so care must be taken to not wander off the narrow trail, and I did spot some animal carcasses in some geysers.
Here are couple more of the geysers...
Immediately beyond the geyser basin heading south, you encounter a mile-long marsh which has you ankle-to-knee deep in marsh water until you finally reach solid ground again. This might be solid trail in a year with less snowmelt, but it wasn't in 1997!
After fording Lewis Channel (which connects Lewis Lake and Shoshone Lake), I was hiking though one of the areas burned by the 1988 fires which affected 793,880 acres of Yellowstone, 36% of the park. $120,000,000 was spent on extinguishing the 51 fires (9 caused by humans and 42 caused by lightening.) If you look at the left of the photo below, you see the narrow trail, and the ground between the snags (dead trees) is loaded with new growth, showing the self-seeded "replacement" forest well underway just 9 years after the fires.
On my visit through YNP in 2014, the new forests throughout the park were densely forested with 15 to 25 foot tall growth growing so close together you couldn't bushwhack though the new growth! I talked to a ranger about this and he excitedly described how these new dense forest areas were ideal habitat for the smaller animals since they now had areas to hide from larger predators. Of course, Nature will thin out these stands as time progresses.
Elevation within Yellowstone ranges from 5282 at Reese Creek to 11,358 at Eagle Peak's summit. There are 110 waterfalls with a drop of 15 feet or greater. Yellowstone gets its name from the high yellow rock cliffs along the upper reaches of the Yellowstone River which are very obvious in the Grand Canyon of the Yellowstone. The Minnetaree Indians called the river "Mi tsi a da zi" or "Rock Yellow River" which was loosely translated by French trappers to "Yellow Rock River" and eventually Yellow Stone River."
Through cooperative efforts, The Greater Yellowstone Ecosystem has been designated and consists of 11 to 22 million acres of land, comprised of Yellowstone National Park, Grand Teton National Park, and the six national forests surrounding them. Over 4000 miles of trails are within this area. Grizzly (approximately 200-250) and black bear are the most talked about wildlife. In addition, though, are 7 species of hoofed mammals (including bison, elk, pronghorn antelope, moose, and mule deer), 49 other species of mammals, 290 species of birds, 18 species of fish, 6 species of reptiles, 4 of amphibians, and 5 endangered/threatened species. Flora include 8 species of conifers (with lodgepole pine the predominant species) as well as over 1050 species of native vascular plants and 168 species of non-native plants.