San Marcos is a city located in the state of California, United States. It is situated in northern San Diego County and is part of the San Diego metropolitan area. San Marcos has a population of approximately 96,000 people as of 2020. The city is known for its suburban feel, excellent schools, and numerous outdoor recreational opportunities, including hiking, biking, and golfing. San Marcos is also home to California State University San Marcos, which is a public university offering a variety of undergraduate and graduate programs.