Sprague's inventions included several improvements to designs for systems of electric streetcars collecting electricity from overhead lines.Middleton, William D. (1966). The Time of the Trolley, pp. 63–73. Milwaukee: Kalmbach Publishing. . He improved designs for a spring-loaded trolley pole that had been developed in 1885 by Charles Van Depoele, devised a greatly improved mounting for streetcar motors and better gear designs, and proved that regenerative braking was practical. After testing his trolley system in late 1887 and early 1888, Sprague installed the first successful large electric street railway system – the Richmond Union Passenger Railway in Richmond, Virginia, which began passenger operation on February 2, 1888. Long a transportation obstacle, the hills of Richmond included grades of over 10%, and were an excellent proving ground for acceptance of his new technology in other cities, in contrast to the cable cars which climbed the steepest grades of Nob Hill in San Francisco at the time.
