San Clemente Island

San Clemente Island is the southernmost of the Channel Islands of California. It is owned and operated by the United States Navy, and is a part of Los Angeles County. It is administered by Naval Base Coronado. It is 21 miles long and has 147.13 km2 of land. The census estimates 148 military and civilian personnel resident on the island in 2018. The city of San Clemente in Orange County, California is named after the island.

Geologically, the island is described as being "the upper part of a tilted and gently arched northwestward-trending block of the earth's crust that has a straight, steep northeastern slope and a more irregular and much gentler southwestern slope" that is composed primarily of volcanic rock, with the northeast boundary of the island having a large fault that parallels most of the major faults on the California mainland. San Clemente Island has some of the best examples of marine terraces, and has trench-like canyons, streams, periodic waterfalls, and pools of fresh water.

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