I used an unscientific formula to “rank” the primary routes from 1920, from the least to the most important. That will be a framework for blog posts about the system. The smallest spurs to the smallest towns, not surprisingly, fill the bottom ranks.
For the routes that lasted after 1980, I expanded their already existing pages and added photos to quite a few. If you try to go to a route in the 1920 series and it doesn’t have its own page, there should be an automatic redirect.
- IA 70, half a mile to Macksburg, leads off the list.
- Spurs that were practically unchanged until 1980 or shortly thereafter: 42, 54, 79, 87, 102
- IA 72 almost fit the above point, but it had changes to the west end and was extended to I-35 for six years.
- Spurs that were practically unchanged until 2003: 36, 41, 68, 82, 97.
- IA 50 was extended into a double spur for decades, but its 1920 and 2003 endpoints were identical.
- Spurs that were unchanged or slightly changed except for a number replacement: 52 (to 272), 67 (to 55), 69 (to 138), 92 (to 363)
- Other routes: 81 (which later became IA 114), 84 (tied into the history of IA 999)