San Diego County is located in the southern part of California, bordered by the Pacific Ocean to the west and the U.S.-Mexico border to the south. It is known for its diverse geography, which includes beaches, mountains, and deserts. The county is home to the city of San Diego, the second-largest city in California, and features numerous parks, including Balboa Park and Torrey Pines State Natural Reserve. The county has a population of over 3 million residents, making it one of the most populous counties in the United States. It is also recognized for its mild climate, with warm, sunny weather year-round. Key industries in the area include tourism, military, and biotechnology.