  the chicago tunnel company built a  narrow gauge railway freight tunnel network under the downtown of the city of chicago. this was regulated by the interstate commerce commission as an interurban despite the fact that it operated entirely under central chicago, did not carry passengers, and was entirely underground.william clark, vanishing in america â interurban trolley, chicago tribune, jul. 6, 1958; page a9. it inspired the construction of the london post office railway.unofficial mailrail website ==history== thumb|200px|1902 system map, tunnels shown in black, construction shafts are dots to the side of the tunnels. the city of chicago granted the newly formed illinois telephone and telegraph company the rights to construct utility tunnels under the streets of chicago in 1899 to carry its planned network of telephone cables. initial plans for the tunnels called for filling them with phone cables, leaving a  by  passage for maintenance. when the city refused to permit manholes through which cable could be unreeled into the tunnels, the plans were changed to include rails for hauling cable spools through the tunnels.george w. jackson, scope, extent and construction of the underground conduits of the illinois telephone and telegraph co. in chicago, presented sept. 17, 1902, journal of the western society of engineers, vol. vii, no. 5 (oct. 1902); page 479. note: illustrated.george w. jackson, tunnel construction: in chicago â method of driving and constructing so as not to disturb the surface, mines and minerals, vol. xxiii, no. 6 (jan. 1903); page 248. note: illustrated.george w. jackson, underground conduits in chicago, page's engineering weekly, vol ii, no. 3 (march 1903); page 317. note: illustrated. the city was largely unaware of the nature of the tunneling, and the first  of tunnel were excavated somewhat covertly, working from the basement of a saloon and carting away the spoil after midnight.obituary, george w. jackson, engineering and contracting, vol. 57, no. 6 (feb. 8, 1922); page 144. initially, the inte
2_ft_gauge_railways_in_the_United_States Defunct_Illinois_railroads History_of_Chicago,_Illinois Narrow_gauge_railroads_in_Illinois Railroads_in_the_Chicago_Switching_District Tunnels_completed_in_1906 Tunnels_in_Illinois