Kauai is geologically the oldest of the main Hawaiian Islands. With an area of 562.3 square miles (1,456.4 km2), it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States.Known also as the “Garden Isle”, Kaua?i lies 105 miles (169 km) across the Kaua?i Channel, northwest of O?ahu. This island is the site of Waimea Canyon State Park.
The United States Census Bureau defines Kaua?i as Census Tracts 401 through 409 of Kaua?i County, Hawai?i, which is all of the county except for the islands of Ka?ula, Lehua, and Ni?ihau. The 2010 census population of Kaua?i (the island) was 67,091, with the largest town by population being Kapa?a.