I am a fan of Exit Zero. Not everyone is.
Mile markers begin at the south or west terminus of a route or the state line. When the route has an interchange at that terminus, it should follow that the exit number correspond to the mile marker, in this case, 0. But often, to avoid confusion with the letter O, the designation will be skipped in favor of Exit 1, making “mile 1” effectively 2 miles in length.
There has been one prominent Exit Zero signed in Iowa: I-380 at I-80, but southbound only. On northbound US 218, the exit is not numbered at all. It should also be 0A-B, or at least 96A-B, corresponding to 218’s miles. Semi-recently, I-480’s eastbound-only exit ramp to Dodge Park (now signed as “Riverfront”) became an Exit 0, while the I-29 interchange is unnumbered.
But now we have another Exit Zero in the field: IA 100’s new west end at US 30/218 in Cedar Rapids. The interchange is intermingled with a complete diamond for 80th Street SW on 30. I found this out via KGAN’s story on the bypass’ opening. There’s also a “100 Ends” sign, but it’s not going to be easy to get.
Although the dedication was Dec. 1, my note that there weren’t any BGSs on 30 then has an explanation behind it: Tariffs made it difficult to get the remaining steel needed, the KGAN story says.