San Diego–Tijuana in the context of "Mexico–United States border"

San Diego County (/ˌsæn diˈeɪɡoʊ/ ), officially the County of San Diego, is a county in the southwest corner of the U.S. state of California, north to its border with Mexico. As of the 2020 census, the population was 3,298,634; it is the second-most populous county in California and the fifth-most populous in the United States. Its county seat is San Diego, the second-most populous city in California and the eighth-most populous in the United States. It is the southwesternmost county in the 48 contiguous United States, and is a border county. It is home to 18 Indian reservations, the most of any county in the United States. There are 16 military installations of the U.S. Navy, Marine Corps, and Coast Guard in the county.

San Diego County comprises the San Diego–Chula Vista–Carlsbad, CA Metropolitan Statistical Area, which is the 18th most populous metropolitan statistical area and the 18th most populous primary statistical area in the United States. San Diego County is also part of the San Diego–Tijuana region, the largest metropolitan area shared between the United States and Mexico. From north to south, San Diego County extends from the southern borders of Orange and Riverside counties to the Mexico–U.S. border and the municipalities of Tijuana and Tecate in Baja California. From west to east, San Diego County stretches from the Pacific Ocean to its boundary with Imperial County, which separated from it in 1907.

Ciudad Juárez (US: /sjuːˌdɑːd ˈhwɑːrɛz/ sew-DAHD HWAR-ez; Spanish: [sjuˈðað ˈxwaɾes] ; "Juárez City"), commonly referred to as just Juárez (Lipan: Tsé Táhú'ayá), is the most populous city in the Mexican state of Chihuahua. It was known until 1888 as El Paso del Norte ("The North Pass").

It is the seat of the Juárez Municipality with an estimated metropolitan population of 2.5 million people. Juárez lies on the Rio Grande (Río Bravo del Norte), south of El Paso, Texas, United States. Together with the surrounding areas, the cities form El Paso–Juárez, the second largest binational metropolitan area on the Mexico–U.S. border (after San Diego–Tijuana), with a combined population of over 3.4 million people.

El Paso–Juárez, also known as Juárez–El Paso, the Borderplex or Paso del Norte, is a transborder agglomeration, on the border between Mexico and the United States. The region is centered on two large cities: Ciudad Juárez, Chihuahua, Mexico, and El Paso, Texas, United States. Additionally, nearby Las Cruces, New Mexico, U.S., is sometimes included as part of the region, referred to as El Paso–Juárez–Las Cruces or El Paso–Juárez–Southern New Mexico. With over 2.4 million people, this binational region is the 2nd largest conurbation (San Diego–Tijuana being the largest) on the United States–Mexico border. The El Paso–Juárez region is the largest bilingual, binational work force in the Western Hemisphere.

This region is commonly subdivided into the Juárez Metropolitan Area (Zona Metropolitana de Juárez) in Chihuahua, Greater El Paso in Texas and Greater Las Cruces in New Mexico. These sub-regions are typically defined by state borders, even though some New Mexico towns in the region like Sunland Park are significantly closer to El Paso than to Las Cruces.

Tijuana is the most populous city of the Mexican state of Baja California, located on the northwestern Pacific Coast of Mexico. Tijuana is the municipal seat of the Tijuana Municipality, the hub of the Tijuana metropolitan area and the most populous city in northern Mexico. It is just south of California and is close to the Mexico–United States border which is part of the San Diego–Tijuana metro area.

Tijuana is the 27th largest city in the Americas and is the westernmost city in Mexico. As of 2024, the population of Tijuana has increased to 2,297,000, reflecting a growth of 1.63% since 2023. The city was second-largest nationally with 1,810,645 inhabitants. The international metropolitan region was estimated at 5,158,459 in 2016, making it the third-largest metropolitan area in The Californias, 19th-largest metropolitan area in the Americas, and the largest bi-national conurbation that is shared between US and Mexico. The city is one of the fastest-growing metro areas in the country and rated as a "High Sufficiency" global city by the Globalization and World Cities Research Network.

Rosarito is a coastal city in Playas de Rosarito Municipality, Baja California, on the Pacific Coast of Mexico. As of 2010, the city had a population of 65,278. Located 10 miles (16 km) south of the US–Mexico border, Rosarito is a part of the greater San Diego–Tijuana region and one of the westernmost cities in Mexico. Rosarito is a major tourist destination, known for its beaches, resorts, and events like Baja Beach Fest.

Tecate (Spanish: [teˈkate] ) is a city in Tecate Municipality, Baja California. It is across the Mexico–US border from Tecate, California. As of 2019, the city had a population of 108,860 inhabitants, while the metropolitan area has a population of 132,406 inhabitants. Tecate is part of the San Diego–Tijuana metropolitan region and the largest city between Tijuana and Mexicali. Tecate is a regional economic hub and popular tourist destination, known as home to the Tecate Port of Entry and to Tecate beer.