 Prior to the 1970s, short spur routes that were offshoots of main highways were given route numbers based on the main highway.The spurs were numbered sequentially from west to east or north to south and prefixed to the main route's number.For instance, the spur from U.S. Highway 6 (US 6) into Champion was numbered Spur 106 and the spur from US 183 into Huntley was Spur 2183.