Grant Keller, age 12, of Henderson, Nevada, for his question:

WHO DISCOVERED YELLOWSTONE NATIONAL PARK?

An American trapper named John Colter discovered and explored the Yellowstone region that now makes up the oldest national park in the United States.

Colter's adventure started in 1803 when he enlisted for the Lewis and Clark expedition near Maysville, Ky. He stayed with the expedition until 1806 to become a mountain man.

Colter planned to join two companions and remain in the upper Missouri River area for at least two years in pursuit of his fortune. For a considerable period, he was lost to civilization. He probably spent his time in the West, wandering along the Missouri River and through the Rocky Mountains.

Colter's greatest activity was along the Yellowstone River. He associated closely with many Indian tribes.

In 1807, Colter was in the Yellowstone basin on a fur hunting expedition. During this period, he made his famous exploring journey into the wild countryside and discovered the great thermal springs area that is now Yellowstone National Park. He also discovered several passes through the Rocky Mountains.

Colter's exploits in the mountains have been a basic source of information about American frontier expansion in that region.

Colter returned to St. Louis in 1810 and retired as a mountain man.

The government established Yellowstone National Park in 1872. Today, more than two million visitors come to the area each year. Most drive through the park, but many explore the large wilderness areas that can be reached only by foot or on horseback.

Yellowstone today has more than 300 miles of roads and over 1,000 miles of trails.

There are five entrances into Yellowstone: two from Wyoming and three from Montana. Each entrance connects with the Grand Loop, a 143 mile road that leads to major points of interest.

Yellowstone's Grand Loop consists of the southern Lower Loop and the northern Upper Loop.

The Lower Loop leads to several geyser basins. Here you'll see the Fountain Paint Pots, a series of hot springs and bubbling pools of mud called mudpots or paint pots. You'll also see the most famous geyser in the park: Old Faithful. This wonderful display of nature presents an eruption of water on the average of every 65 minutes.

Also on the Lower Loop is the Grand Canyon of the Yellowstone. It cuts across the landscape for about 20 miles and reaches a depth of about 2,000 feet. The Yellowstone River runs through the canyon.

The Upper Loop leads north from Grand Canyon of the Yellowstone through the mountains of the Washburn Range with the 10,243 foot mount Washburn rising on the east.

Here also you'll find Norris Geyser Basin that is made up of hundreds of geysers, hot springs and pools. It is the hottest and most active thermal area in Yellowstone. Steamboat Geyser here set a world record by hurling its water 400 feet into the air.