California Borders: States, Map & Complete Guide

Oregon and California are separated by a border located on California's northern edge. The state line follows the 42nd parallel north latitude, creating a straight east-west boundary across the top of California.

The California-Oregon border extends from the Pacific Ocean in the west to the Nevada state line in the east. Several California counties are situated along this border including Del Norte, Siskiyou, and Modoc. On the Oregon side, counties along the border include Curry, Josephine, Jackson, and Klamath.

Nevada and California share California's longest state border, located on California's eastern side. The boundary follows a diagonal line that runs roughly northwest to southeast through the Sierra Nevada mountains.

This border region includes Lake Tahoe, which straddles the California-Nevada line in the northern section. Several important California counties are situated along this border including Placer, El Dorado, Alpine, Mono, and Inyo. The eastern border also includes Death Valley National Park, which extends into Nevada.

Arizona and California are separated by a border located on California's southeastern edge. The Colorado River forms most of this boundary, creating a natural border for about 240 miles before the river flows into Mexico.

This river boundary makes the California-Arizona border unique among California's state borders. Major communities along this border include Needles, Blythe, and Yuma (on the Arizona side). Several California counties are situated along the border with Arizona including San Bernardino, Riverside, and Imperial.

Mexico is the only country that shares a border with California. The international boundary runs roughly 140 miles from the Pacific coast near San Diego east to the Colorado River.

The border touches two Mexican states—Baja California and a small section of Sonora near the Colorado River. Major crossing points along the California-Mexico border include San Ysidro (the busiest land border crossing in the Western Hemisphere), Otay Mesa, Calexico, and Tecate.

The Pacific Ocean forms California's entire western boundary, providing approximately 840 miles of coastline. This extensive coastline stretches from the Oregon border in the north to Mexico in the south.

California's Pacific coast includes diverse geography from rocky cliffs in Big Sur to sandy beaches in Southern California. Major coastal cities include San Francisco, Los Angeles, and San Diego, all of which developed around natural harbors along this coastline.