The San Francisco cable car system is the world's last manually operated cable car system and an icon of the city of San Francisco. The system forms part of the intermodal urban transport network operated by the San Francisco Municipal Railway, which also includes the separate E Embarcadero and F Market & Wharves heritage streetcar lines, and the Muni Metro modern light rail system. Of the 23 cable car lines established between 1873 and 1890, only three remain (one of which combines parts of two earlier lines): 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 the millions of passengers who use the system every year are tourists, and as a result, the wait to get on can often reach two hours or more. They are among the most significant tourist attractions in the city, along with Alcatraz Island, the Golden Gate Bridge, and Fisherman's Wharf. San Francisco's cable cars are listed on the National Register of Historic Places and are designated as National Historic Landmarks. In 1869, Andrew Smith Hallidie had the idea for a cable car system in San Francisco, reportedly after witnessing an accident in which a streetcar drawn by horses over wet cobblestones slid backward, killing the horses. Hallidie solicited financial support in 1871 and 1872, and his primary backers were Henry L. Davis, Joseph Britton, and James Moffit. The first successful cable-operated street running train was the Clay Street Hill Railroad, which had its inaugural run on August 2, 1873. The promoter of the line was Hallidie, and the engineer was William Eppelsheimer; both Hallidie and Eppelsheimer obtained several patents for their work on the Clay Street line. The line involved the use of grip cars, which carried the grip that engaged with the cable, towing trailer cars; the design was the first to use grips. The term "grip" became synonymous with the operator. The line started regular service on September 1, 1873, and its success led it to become the template for other cable car transit systems. It was a financial success, and Hallidie's patents were enforced on other cable car promoters, making him wealthy. (Wikipedia, 2022)