Kauaʻi is geologically the oldest of the main Hawaiian Islands. With an area of 562.3 square miles , it is the fourth largest of these islands and the 21st largest island in the United States.

Known also as the "Garden Isle", Kauaʻi lies 105 miles across the Kauaʻi Channel, northwest of Oʻahu. This island is the site of Waimea Canyon State Park.

The 2010 US Census reported the population of the island at 67,091. The most populous town was Kapaʻa.