Congaree National Park, South Carolina

Congaree National Park safeguards the largest intact old-growth bottomland hardwood forest in North America, with canopy heights averaging 100–130 feet—surpassing #3 Guadalupe Mountains' highest peak in vertical forest structure. Its Champion Tree Trail features loblolly pines exceeding 500 years old, and the synchronous firefly event each May draws 10,000+ visitors to witness a bioluminescent display 50% brighter than the average firefly swarm elsewhere. This park's 26,000 acres flood annually, depositing nutrient-rich silt that fuels tree growth rates 30% faster than the typical park ecosystem, making it a hidden gem for biodiversity.