— John Steinbeck, author, in “Travels with Charley: In Search of America”

“[It] is no more representative of America than is Disneyland.”

Size 2,219,791 acres

2,219,791 acres Founded 1872

1872 Attendance 4,097,710

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This, the first U.S. national park, in part owes its physical asset to the active volcano that lies beneath its surface, where the Park Service says there’s enough magma to fill the Grand Canyon about 11 times.

Seismologist Robert B. Smith has described the park as “an active geologic laboratory — and the laboratory is alive.”

That living landscape speaks through 10,000 hydrothermal features: hissing fumaroles (steam vents), spewing geysers and gurgling mud pots. Old Faithful geyser, the most well-known, erupts about 17 times a day.

The subterranean side of Yellowstone is what the Park Service has called a pressure cooker. Aboveground, much of Yellowstone is a protected paradise. Its beauty became widely known when photographer William Henry Jackson documented the region for the U.S. Geological and Geographical Survey of the Territories. His images helped inspire Congress to establish the park.

Yellowstone is large, with 17 rivers, 290 waterfalls, five entrances, 4,000 bison and acreage spanning portions of three states (96 percent in Wyoming, 3 percent in Montana and 1 percent in Idaho). It has the largest lake on the continent at a high elevation (7,733 feet).

Yellowstone is home to the largest concentration of mammals in the lower 48. In addition to bison, those inhabitants include grizzly bears, wolves, lynxes, foxes, moose and elk.

Humans also have left their mark on this western range. It has 26 associated Native American tribes, 466 miles of roads (310 miles paved) and more than 900 historic buildings. Included among those vintage structures are Old Faithful Inn and the Lake Hotel, built in 1891, the oldest operating hotel in the park.

Also here is an unexpected category: “other life forms.” That “other” is heat-loving bacteria, which create the ribbons of color in hot water.

As the Park Service explains, the green, brown and orange mats are cyanobacteria, which can thrive in waters as hot as 167 degrees. Here, the colors are visible in the Grand Prismatic Spring at Midway Geyser Basin. Grand Prismatic is the largest hot spring in the country and the third largest in the world.

In 1871, well before color photography could document the vibrant phenomenon, Ferdinand Hayden, leader of the U.S. Geological Survey expedition, described the hot spring’s “peculiar vividness and delicacy of color [from] nature’s cunning skill.”

[Yellowstone National Park: endless photographic possibilities]