Book excerpt: With today's America dominated by the automobile, it is difficult to believe that until the 1920s nearly 100 percent of the US population traveled via rail. Conventional passenger-train service spread rapidly by the 1850s, but another form of rail transportation did not emerge until the turn of the 20th century: the interurban. Almost always electric, interurbans linked cities with burghs. Rockford, one of Illinois's three largest urban centers during the 20th century, enjoyed a system appropriately named the Rockford & Interurban, dating from the city's horse-drawn streetcars of the 1880s. By World War I, the Rockford & Interurban ran from downtown Rockford to Cherry Valley and Belvidere; Winnebago, Pecatonica, and Freeport; Roscoe and Rockton; and Beloit and Janesville, Wisconsin. The Rockford & Interurban enjoyed a supernova of success, rising quickly in popularity before slowly dying when the automobile became widespread in the 1920s; the Great Depression finished the job in 1936.