US10 and US12 in Wisconsin in the early years

[invincor]

As many probably know, when the US highway system was first laid out, US10 and US12 shared roadway from St. Paul, MN to Osseo, WI, mostly along what is US12's present-day route.  I understand this was because there was no bridge in Prescott, WI yet, where 10 presently crosses the state line and St. Croix River.  I also think some of the rest of the present 10 route in western Wisconsin wasn't improved yet either. 

That bridge got built in 1931, iirc, and when the system had its big revision of numbers in 1935 or so, they moved 10 south to its present-day route.  In so doing, they violated the numbering convention, as now 10 is out-of-sequence over that stretch.  If they'd stuck to that, 10 would've stayed north and 12 would've been moved down to Prescott-Ellsworth-Durand-Osseo.  Does anyone know for sure why it was done the way it was? 

My own guess is that they wanted the one continuous route from Chicago to Madison to the Twin Cities, namely US12, to also take in Eau Claire along the way, as that's the largest "city" in that part of the state. 

Does anyone know for certain, though?

[TheHighwayMan3561]

Maybe it seemed like a natural progression with how those routes aligned west of the Twin Cities, with US 10 following a NW-SE path in the state and 12 a much more east-west line. Then 10 continues to the SE to Hastings before turning east, and 12 continues due east toward Eau Claire.

[The Ghostbuster]

Originally, the present-day US 10 corridor between Prescott and Humbird was designated STH-34 in 1918 (although this designation only went from Ellsworth and Mondovi at that time). In 1923, STH-34 was renumbered as an extension of STH-18, which originally was a Humbird-to-Manitowoc state highway (and was now a Prescott-to-Manitowoc route). In 1926, with the debut of the US Highway System, STH-18 was replaced by US 10 from Humbird-to-Manitowoc, while the Humbird-to-Prescott segment was renumbered back to STH-34 (from 1923-1926, STH-34 went from Berlin-to-Buttes Des Morts). I was not aware that US 10 followed US 12 because there was no bridge connecting Prescott with Point Douglas, but it makes sense to me why US 10 was rerouted after the bridge was constructed. Also, it freed up the STH-34 designation to replace STH-45 between Wisconsin Rapids and Knowlton when US 45 was extended from Chicago, IL to Ontonagon, MI (route duplication between State Highways, US Highways and Interstate Highways were forbidden in Wisconsin prior to the 1990s).

[SEWIGuy]

Before US routes made it to Wisconsin, what became US-12 was WI-12. Probably easier to keep the number on its route rather than cause confusion.

[invincor]

Before US routes made it to Wisconsin, what became US-12 was WI-12. Probably easier to keep the number on its route rather than cause confusion.

Ah, yes, I was forgetting this.  This is probably a big part of it.  Thanks.

[The Ghostbuster]

I find it ironic that US 12 in Wisconsin replaced STH-12 along its entire length. Just like the now-decommissioned US 16 in Michigan replaced M-16 in its entirety within that state.