July 15, 2007: Despite the difference in digits, these shields are the same size around. The east end of IA 8 is one of the few places left in Iowa where you see square US 218 shields as you drive the latter route.
In about the middle of the decade, Iowa started moving toward larger shields at two scales: Wide shields (3 feet wide by 2 feet high) for all three-digit routes, and jumbo signs on four-lane roads. (Ironically, this has not been applied to interstates…yet.) In my opinion, the wide shield is wildly unnecessary, especially in Iowa, where only one three-digit US route does not have a 1 in it.
With mass replacements going on across the state, there are only three segments of US 218 where wide shields are not the order of the day: Between the IA 57/58 interchange and US 30, along I-380, and the short final standalone segments from Donnellson to Keokuk. But with a February sign letting for southeast Iowa, the latter isn’t going to be in this case for long. The 218 shields in the city of Keokuk, and all the US 136 shields, aren’t included in that letting, so they’ll stay for now.
Since the bulk of 218’s entire route is in Iowa, replacement like this will spell the end for the squares — but they won’t be gone entirely. All of the county roads that intersect 218 — including those from the Second Great Decommissioning — retain the squares. We just won’t see them on the mainline while traveling the route.