Native Hawaiian yellow hibiscus brackenridgei (ma`o-hau-hele flower); photo by Rosa Say on Flickr (noncommercial use permitted with attribution / no derivative works).
Official State Flower of Hawaii
Hawaii designated yellow hibiscus (Hibiscus brackenridgei), also known as Pua Aloalo or Ma`o-hau-hele, as the official state flower in 1988. All State Flowers
Yellow hibiscus is found only in Hawaii - it grows on all the main Hawaiian islands, but it's extremely rare (so few remain in the wild, that it's considered an endangered species).
Official Island Flowers
Each Hawaiian island also designates an official flower or lei material (as well as an official island color):