The San Francisco Fire Department, along with the San Francisco Police Department and San Francisco Sheriff's Department, serves an estimated population of 1.4 million people, which includes the approximately 850,000 citizens residing in the 47 sqmi of San Francisco (including Treasure Island, Yerba Buena Island, San Francisco-Oakland Bay Bridge, Golden Gate Bridge, Alcatraz Island, the San Francisco International Airport, and the Presidio of San Francisco/Golden Gate National Recreation Area.