Mammoth Cave National Park is home to the world's longest known cave system.

The Great Smoky Mountains National Park is a vast area of pristine wilderness, spanning more than half a million acres.

The Gateway Arch National Park is renowned for its iconic stainless steel arch.

The Cuyahoga Valley National Park is a sprawling nature reserve encompassing more than 33,000 acres.

Congaree National Park preserves the largest tract of old growth bottomland hardwood forest in the United States.

Hot Springs National Park, a popular tourist destination, is known for its naturally heated springs.

The Shenandoah National Park covers an area of over 200,000 acres.

Isle Royale National Park is a remote island cluster in Lake Superior and the home for various wildlife like wolves and moose.