Border Field State Park is on the very southwestern corner of the United States and 15 miles south of San Diego. Border Field is located within the Tijuana River National Estuarine Research Reserve, an important wildlife habitat. The sand dunes and salt marshes give refuge to critically threatened and endangered birds such as the Western Snowy Plover, the California Least Tern, and the Light-footed Clapper Rail.
The park provides restrooms, picnic areas, barbecues, horse corrals, and interpretive displays. Visitors enjoy beach combing, hiking, horseback riding, and bird watching. The Park does not recommend swimming or wading, due to hazardous conditions, such as inshore holes, rip currents, and the lack of lifeguard service within the Park.
The Treaty of Guadalupe Hidalgo was concluded on February 2, 1848, officially ending the U.S./Mexico War. In 1850, delegations from both countries began surveying the boundary at this location. Border Monument number 258 can be viewed from Monument Mesa, however there is no close access because it is now behind two border fences.