| State: | IL |
| Type: | IL |
| Map Custom: | yes |
| Map Notes: | Illinois Route 73 highlighted in red |
| Maint: | IDOT |
| Route: | 73 |
| Length Mi: | 29.32 |
| Length Round: | 2 |
| Direction B: | North |
| Direction A: | South |
| Terminus A: | in Lanark |
| Terminus B: | CTH M in Winslow |
| Junction: | in Lena |
| Counties: | Carroll, Stephenson |
| Established: | 1924[1] |
| Previous Route: | 72 |
| Previous Type: | IL |
| Next Route: | 74 |
| Next Type: | I |
Illinois Route 73 is a north - south state highway in northwest Illinois. It runs from the U.S. Route 52/Illinois Route 64 concurrency south of Lanark north to the Wisconsin border north of Winslow. This is a distance of 29.32miles.[2]
Illinois 73 is a two-lane surface road for its entire length. At its northern terminus, Illinois 73 becomes County Highway M in Green County, Wisconsin. This is the only Illinois state highway that does not either continue as another state highway, or end at a ferry crossing (current or former).[1]
SBI Route 73 existed from Illinois Route 72 north of Lanark to Winslow. Around 1982, it replaced Illinois 72 from north of Lanark south to U.S. Route 52.[1]