[2][3] It is the westernmost island in California[4] It is part of South Cape Mendocino State Marine Reserve, a large protected marine reserve centered on Cape Mendocino fully protected by the California Department of Fish and Wildlife.

The area is one of the most undeveloped sections of the California coast, and its waters are home to important bird and mammal species.

[6] Sugarloaf Island is covered by the Cape Mendocino, California U.S. Topographic Map quadrant.

The area provides essential habitat and breeding grounds to the Steller sea lion and its rocky outcroppings also provide resting places for California sea lions.

[7] While it is sometimes confused with "Sugarloaf Rock," the latter is found in the Farallon Islands offshore San Francisco, several hundred miles distant.