23. Redwoods National Park, California

Annual visitors: 482,536

Fun fact: The Smith River that flows through the park is the longest undammed river in California.

Strolling through the massive redwood trees of this old-growth forest is akin to a spiritual experience. After mass deforestation during the Gold Rush and later during World War II, when the need for timber was high, the untouched wilderness of the Redwoods Park is especially rare and precious; 96% of the trees that originally covered 2 million acres in California have been logged. You can’t camp inside the park, but you can stay nearby and explore on horseback, by kayak, or on hiking trails that venture to the area’s natural splendors, like Fern Canyon.