Hot Springs National Park

Forty years before Congress created Yellowstone, it had already set aside federal land for exactly the same reason: in 1832, lawmakers reserved four sections of land around the hot springs of what is now Hot Springs, Arkansas, making it the oldest federally protected land in the entire National Park System, decades before the term "national park" existed anywhere in American law. Andrew Jackson's administration oversaw the reservation, protecting 47 thermal springs that flowed from Hot Springs Mountain at a near-constant 143 degrees, land that many Native nations, including the Quapaw and Caddo, had treated as neutral ground where rival peoples could bathe and heal without fear of attack.

The reservation grew into a full-blown resort town rather than a wilderness, as bathhouses, hotels, and bottling operations sprang up around the springs through the 19th century under loose federal oversight that courts and Congress spent decades trying to clarify. The federal government built and regulated a row of ornate bathhouses, known today as Bathhouse Row, that drew the wealthy and, at points, gangsters and gamblers attracted to the town's loosely enforced vice laws in the early 20th century. Congress finally redesignated the reservation as Hot Springs National Park in 1921, folding a site that had functioned for nearly a century as a federal spa into the same legal category as Yellowstone and Yosemite.

Hot Springs remains one of the smallest and strangest parks in the system, with a historic downtown and working bathhouses sitting inside its boundary rather than a backcountry gateway. The Buckstaff Bathhouse has operated continuously on Bathhouse Row since 1912, letting visitors still soak in the same thermal water that federal officials set aside for the public nearly two centuries ago, long before anyone had imagined a national park.