The Fox and Illinois Union Railway was an interurban line that intended to link communities along the Fox and Illinois Rivers, as its name suggests. However, only a portion of the route between Yorkville (on the Aurora, Elgin and Fox River Electric Railway) and Morris (on the Chicago and Illinois Valley Railway) was built in 1911. The line ran due south along Illinois Routes 47 and 71. A power substation was located at Walker's Crossing (Walker Road and Route 47), and there were sidings in Kendall County at Lisbon Center, Kentland, and Central in Kendall County to serve the grain elevators located there.
At the Morris end of the line, the tracks passed under the Rock Island Railroad before ending with a connection at the Chicago Ottawa & Peoria Electric Railway at the Hotel Commercial. The line's connection to the Rock Island was located on the north edge of Morris, where there was also a siding at the old Quaker Oats Company plant.
On Jan. 31, 1925, the AE&FR abandoned interurban service between Aurora and Yorkville, cutting off passenger access to Aurora and Chicago. In February of 1931, the F&IU was permitted to stop its passenger service and turn into a freight line servicing the grain elevators between Morris and Yorkville. Eventually, the line was killed as, after the Great Depression, roads improved and farmers were able to buy their own trucks and cars. The Fox and Illinois Union Railway was finally abandoned on Oct. 15, 1938.