This website tells the story about a 60-mile, two-foot gauge electric railroad that operated 149 locomotives and over 3000 freight cars in small tunnels forty feet below the streets of downtown Chicago.
The Illinois Tunnel Company ( later known as the Chicago Tunnel Company) started operating trains through the freight tunnels in 1906. The small four wheel electric locomotives hauled pony freight cars between stores, office buildings, post office facilities, warehouses, factories, and railroad stations. The tiny cars carried packages, goods, mail, food, coal, cinders, and occasionally people!