Hawaii Volcanoes National Park boasts living marvels found nowhere else on earth. Visitors can spot a showy Kamehameha butterfly by mamaki trees, and admire one of Hawaii Island’s rarest plants, the hibiscus-like hau kuahiwi. In all, the park hosts 26 endangered or threatened endemic plant species, including the Mauna Loa silversword. Golden Gate National Recreational Area, the nation’s largest urban park, also has among the highest number of endangered plant and animal species. Teeming tidal pools and more than 100 sea caves stud the rocky California coast, where brown pelicans dive for dinner.