Mount Rainier National Park, Washington

The mighty Mount Rainier is the world's 21st most prominent mountain and highest in the lower 48 states. Considered an active volcano, Mount Rainier's last eruption was in 1894, but its many small, high-frequency earthquakes occur as often as five times a day. The surrounding volcanic soil is so fertile that wildflower meadows ring the icy volcano's 25 glaciers and lush ancient forests cloak the lower slopes. With a rich ecosystem that supports abundant wildlife, a world of discovery awaits each outdoor adventurer, young and old. And never mind those rumbling sensations; they are probably just the tingling heartbeats of excitement as you embrace your wild side.