Aerial view of Grand Prismatic Spring, Yellowstone National Park, Wyoming

'America's best idea' began here. National Park Week begins

Only a very small percentage of Yellowstone's total visitors see the park when it looks like this. In winter, when the park grows quiet, its hydrothermal features really stand out, like the rainbow-hued Grand Prismatic Spring in the bottom center of this image, the most photographed feature in Yellowstone.

Just the inspiration we need as we start National Park Week, an occasion to celebrate the splendor of our park system and turn to thoughts of hiking, paddling, and camping. The 'week' is actually a bit longer, starting today and running through Sunday, April 24. Yellowstone was established by Congress 150 years ago as the nation's first national park. Today, there are 63, and they include the volcanoes of Hawaii, the giant sequoias of California, the Grand Canyon, and the desolate moonscape of the Badlands.

Perhaps no national park better captures the American landscape than Yellowstone, 3,500 square miles of lakes, canyons, rivers, mountains, waterfalls, hot springs, and its charismatic megafauna—bison, wolves, elk, and grizzly bears. But it's Yellowstone's hydrothermal sites that really set it apart. Old Faithful might be the most famous of them, but it's only one of 10,000 geysers and hot springs around here. Because the park is still chilly in April, you'll have the place mostly to yourself. Only about 44,000 people visit Yellowstone in April, compared to the nearly 1 million who gather each July. If you need more incentive, entrance fees today, in honor of National Park Week, are on the house.