October 22, 2014: So what do we do with these brand-new signs now? Put H10 markers in the IA 370 spots, I hope.
At some point during the past week, IA 370 was decommissioned in Mills County. The state-maintained connection between I-29 and the Missouri River toll bridge is not vital after the new US 34 bridge opened not quite a month ago. This had been a foreordained conclusion, with the transfer-of-jurisdiction vote back in January 2010 (PDF).
The decommissioning of Iowa’s second-highest numbered and signed state highway leaves four 300-number routes. For the time being, NE 370 still exists all the way to the river, and remains a high-numbered anomaly in that state.
Dan Drackley spotted the change in signs.