San Quentin is a well-known prison located in Marin County, California. However, there are several synonymous terms that are used to refer to this infamous prison. Some of the synonyms for San Quentin include "The Q," "SQ," "The Rock," and "The Big House." These terms are often used by law enforcement officials, inmates, and members of the public alike when referring to San Quentin. While each nickname has a unique story behind it, they all represent the notorious reputation that San Quentin has gained over the years as a maximum-security prison where some of the most dangerous criminals in California are held.