It was Andrew Smith Hallidie, a Scottish engineer, who first saw the need for a mechanism method of hauling cargo and people up and down the hilly and sloped streets of San Francisco in the late 1860s. Hallidie had used wire rope to design a bridge across the American River in Sacramento as well as for pulling heavy ore cars out of the underground mines in the California mountains. He conceived of the cable car using grips (a clamping device) which he patented in January of 1871. Using these metal ropes he patented, Hallidie devised a mechanism so that cars were drawn using an endless cable running in a slot between the rails. Those cable rails passed over a steam-driven shaft in the powerhouse. The first successful line in San Francisco was called the Clay Street Hill Railroad which began running on August 2, 1873 with full scheduled service starting on September 1st.
San Francisco’s cable system is the only one in the world to endure to the present day. Thanks is largely due to the efforts of the Citizen’s Committee to Save the Cable Cars. In 1947 the mayor planned to close down the cable car system. When committee members heard of the mayor’s plan, they rallied the citizens of San Francisco to cast their votes for an amendment to save the cable cars. The amendment, which passed easily, required a majority vote of the city’s citizens before the cable car system could be closed down in the future.
In 1964 San Francisco's current cable car system was designated a special, "moving" National Historic Landmark. Then they were added to the National Register of Historic Places in 1966. By being on the official list of America's historic places, they are protected by the National Park Service.
The entire system was rebuilt in 1982 and all of the historic cars were refurbished.
The cars, each weighing about 6 tons, run along a steel cable, enclosed under the street in a center rail. You can't see the cable unless you peer straight down into the crack, but you'll hear its characteristic clickity-clanking sound whenever you're nearby. The cars move when the gripper (not the driver) pulls back a lever that closes a pincer like "grip" on the cable. The speed of the car, therefore, is determined by the speed of the cable, which is a constant 9 1/2 mph.
There are currently 40 cars in service: 28 “single-enders” serve the Powell Street routes and 12 “double-enders” serve the California Street route. The cables pull up to 26 cars at a time on weekdays. The cars have a capacity of carrying more than 60 people, and an astounding 7.5 million passengers ride these cars each year.
The San Francisco cable cars are often quoted on fact sites as "The only mobile National Monuments, in the United States.", this is not true. Many other National Monuments are mobile, most notably are the many ships listed in the registry.