Molokaʻi developed from two distinct shield volcanoes known as East Molokaʻi and the much smaller West Molokaʻi. The highest point is Kamakou on East Molokaʻi, at 4,970 feet (1,510 m). Today, East Molokaʻi volcano, like the Koʻolau Range on Oʻahu, is what remains of the southern half of the original mountain. The northern half suffered a catastrophic collapse about 1.5 million years ago and now lies as a debris field scattered northward across the bottom of the Pacific Ocean. What remains of the volcano on the island include the highest sea cliffs in the world. The south shore of Molokai boasts the longest fringing reef in the U.S. and its holdings—nearly 25 miles (40 km) long.
Molokaʻi is part of the state of Hawaiʻi and located in Maui County, except for the Kalaupapa Peninsula, which is separately administered as Kalawao County. Maui County encompasses Maui, Lānaʻi, and Kahoʻolawe in addition to Molokaʻi. The largest town on the island is Kaunakakai, which is one of two small ports on the island. Molokai Airport is located on the central plains of Molokaʻi.
The United States Census Bureau divides the island into three census tracts: Census Tract 317 and Census Tract 318 of Maui County, Hawaiʻi, and Census Tract 319 of Kalawao County, Hawaiʻi. The total 2010 census population of these was 7,345, living on a land area of 260.02 square miles (673.45 km2). Molokaʻi is separated from Oʻahu on the west by the Kaʻiwi Channel, from Maui on the southeast by the Pailolo Channel, and from Lānaʻi on the south by the Kalohi Channel.