Border Field State Park is within the Tijuana River National Estuarine Research Reserve situated adjacent to the urban neighborhood of Playas de Tijuana, Mexico, about 12 miles (19 km) south of San Diego and within the city limits of Imperial Beach, California. Playas de Tijuana is the westernmost borough of the municipality of Tijuana, Baja California. The Tijuana River starts at an elevation of 614 feet (187 m) in the Sierra de Juárez and flows generally west for 120 miles (193 km) draining an arid watershed of 1,119,999 acres (453,247 ha). The river flows intermittently during rains and is naturally prone to flooding. Most of the floodplain consists of poorly consolidated alluvium of silt, sand, and cobble-sized particles. The river is impounded in Mexico for drinking water and irrigation, and the lower river channel is constrained by concrete barriers to prevent flooding. The United States adopted a dissipator flood control plan which preserved the river estuary which was subsequently designated an estuarine research reserve and wildlife sanctuary. The lower river provides the last undeveloped coastal wetlands in Southern California and has been the subject of great controversy in recent decades regarding pollution, flood control, and U.S. border protection.
The Tijuana River National Estuarine Research Reserve provides protected salt and freshwater marsh habitat for migrating waterfowl and resident wading birds, such as black-necked stilt, American avocet, green-winged teal, American wigeon, and pelicans. Border Field State Park represents the southernmost part of the reserve and includes the International Friendship Park, a 0.5 acre (0.2 ha) binational park just inland from where the border enters the ocean. The original intent was to create a place where people from each side of the border could meet under the supervision of the U.S. Border Patrol. The park historically was part of the Monument Mesa picnic area which is the location of a marble monument that was erected at the western end of the border near the Pacific shoreline in 1894. Today, the monument stands on the Mexican side of the border wall and is part of the Plaza Monumental de Tijuana which includes the Tijuana Lighthouse and a bullring popularly known in English as the Bullring by the Sea. It is currently used for bullfighting but has also been used for boxing matches, concerts, and cultural and sporting events. The stadium first opened in 1960 and is located just 200 feet (60 m) from the Mexico-United States border.
In 1848, the Treaty of Guadalupe Hidalgo officially ended the Mexican-American War and provided that the new international border between the two countries be established by a joint boundary survey that began at Border Field. According to the treaty, the initial border point is set as 3 nautical miles (5.6 km) south of the southernmost point of San Diego Bay, and the border proceeds in a straight line towards the confluence of the Colorado River and Gila River about 140 miles (225 km) east near Yuma, Arizona. Until 1994, the border was marked by a simple barbed wire fence, but then amidst widespread fear of illegal immigration, 14 miles (23 km) of steel mesh fence were constructed, but people on opposite sides of the border were still able to touch and pass objects through the barrier. In 2009, the U.S. Department of Homeland Security closed Friendship Park and a second parallel fence was built that extends into the ocean. In late 2011, a surf fence extended the barrier another 300 feet (91 m) into the ocean and the park was reopened for limited hours on weekends. In 2022, a new border wall was approved that was expected to permanently close the U.S. side of Friendship Park. Read more here and here. Explore more of Border Field State Park and Playas de Tijuana here: