San Francisco's Fillmore Street Hill was a one-of-a-kind streetcar operation. When a car reached the bottom of the hill, it waited for an opposing car to reach the top of the hill. Then the two cars were connected to each other by a cable under the street and the downhill car raised the uphill car. When there was no opposing car, such as the last car at night, there was a "sled" counterweight that acted as the opposing car.
Courtesy the Bill Volkmer collection