The San Francisco cable car system is the world's last manually operated cable car system. An icon of San Francisco, the cable car system forms part of the intermodal urban transport network operated by the San Francisco Municipal Railway. Of the 23 lines established between 1873 and 1890, only three remain : two routes from downtown near Union Square to Fisherman's Wharf, and a third route along California Street. While the cable cars are used to a certain extent by commuters, the vast majority of their 7 million annual passengers are tourists. They are among the most significant tourist attractions in the city, along with Alcatraz Island, the Golden Gate Bridge, and Fisherman's Wharf. The cable cars are listed on the National Register of Historic Places.