The crossword solutions for the term MATEO with the clue SAN (3 letters) is SAN. SAN Mateo is a city in California located in the SAN Francisco Bay Area. It is the county seat of SAN Mateo County and has a population of over 100, 000 people. SAN Mateo is known for its diverse economy, which includes technology, finance, retail, and healthcare. The city is also home to several universities and colleges, making it an attractive destination for students.