A Nature Walk Bordering the Tijuana River Estuary

This beach trail begins at the very southwest corner of America, at the monument marking the border between Mexico and California. When California became a territory at the end of the Mexican-American War, an international border became a necessity. American and Mexican survey crews determined the boundary and the monument of Italian marble was placed in 1851 to mark the original survey site. Today the monument stands in the shadow of the Tijuana Bull Ring and still delineates the border between the United States and Estados Unidos Mexicanos.

During World War II the Navy used Border Field as an air field. Combat pilots received gunnery training, learning to hit steam-driven targets that raced over the dunes on rails called Rabbit Tracks.

Before you walk down the bluffs to the beach, take in the panoramic view: the Otay Mountains and San Miguel Mountains to the east, Mexico’s Coronado Islands out to sea, and to the north--the Tijuana River flood plain, the Silver Strand, Coronado.

Much of the Tijuana River Estuary, one of the few salt marshes left in Southern California and one of the region’s most important bird habitats, is within Border Field’s boundaries.

This hike explores the dune and estuary ecosystems of the state park and takes you to wide sandy Imperial Beach. Wear an old pair of shoes and be prepared for the soft mud of the marshland.

Directions to trailhead: Border Field State Park is located in the extreme southwestern corner of California, with Mexico and the Pacific Ocean as its southern and western boundaries. From Interstate 5 (San Diego Freeway) south, exit on Hollister Street, proceed to a T-intersection, bear west (right) 2 miles on Monument Road to the state park. The park closes at sunset.

The hike: Follow the short bluff trail down to the beach, which is under strict 24-hour surveillance by the U.S. Border Patrol. The beach is usually deserted, quite a contrast to crowded Tijuana Beach a few hundred yards south. As you walk north on Border Field State Park’s 1 1/2-mile-long beach, you’ll pass sand dunes anchored by salt grass, pickleweed and sand verbena. On the other side of the dunes is the Tijuana River Estuary, an essential breeding ground, feeding and nesting spot for more than 170 species of native and migratory birds. At Border Field, the salt marsh is relatively unspoiled, unlike many wetlands encountered farther north, which have been drained, filled, or used as dumps.

Take time to explore the marsh. You may spot a marsh hawk, brown pelican, California gull, black-necked stilt, snowy egret, western sandpiper and American kestrel--to name a few of the more common birds. Fishing is good for perch, corbina, and halibut both in the surf along Border Field Beach and in the estuary.

A mile and a half from the border you’ll reach the mouth of the Tijuana River. Only after heavy storms is the Tijuana River the wide swath pictured on some maps. Most of the time it’s fordable at low tide, but use your best judgment.

Continue north along wide, sandy Imperial Beach, past some houses and low bluffs. Imperial Beach was named by the South San Diego Investment Co. to lure Imperial Valley residents to build summer cottages on the beach. Waterfront lots could be purchased for $25 down, $25 monthly and developers promised the balmy climate would “cure rheumatic proclivities, catarrhal trouble, lesions of the lungs,� and a wide assortment of other ailments.

In more recent times, what was once a narrow beach protected by a seawall has been widened considerably by sand dredged from San Diego Bay. There’s good swimming and surfing along Imperial Beach and the waves can get huge. The beach route reaches Imperial Pier, built in 1912 and the oldest in the county.

If you’re feeling especially frisky, you may hike on to Silver Strand. Otherwise, return the same way.

Border Field Trail

Border Field State Park to Tijuana River: three miles roundtrip.

Border Field State Park to Imperial Beach: six miles roundtrip.