Cuyahoga Valley National Park, Ohio

Cuyahoga Valley National Park, the only US national park born from fire, protects 33,000 acres of river gorge that ignited in 1969 due to pollution—sparking the creation of the Environmental Protection Agency just 18 months later. Today, its 125 trail miles see 2.2 million annual visitors, making it 10 times busier than #2 Great Basin, yet its 45-minute proximity to Cleveland and Akron offers accessibility unmatched by any park in the top 5. The Cuyahoga River now hosts 40+ fish species, a 90% recovery from the zero-species count in 1968, showcasing a restoration 50% faster than the average post-industrial watershed.