San Diego County is the southernmost county of California. Located along the Mexican-American border, San Diego County has a population of 3,298,634 inhabitants as of 2020, making it the second most populated county in California by population. The county seat of San Diego County is the city of San Diego, which is home to 1.4 million residents.
Its best known for its mild climate that resembles the Mediterranean coastline. The county is also long associated with the United States Navy. The San Ysidro Border Crossing, located in the southern portion of San Diego County, is the world’s busiest border crossing.