I hadn't noticed this on us-highways.com before, but Rob Droz writes that in 1940 (the same year US 63 was extended south from Turrell AR to West Memphis), there was a proposal to extend US 63 further south, all the way to "coastal Louisiana". Apparently AASHTO rejected the proposal. Does anyone have the details on the proposed route?
This is the first I've ever heard of this.
I finally found the details about this proposal. Turns out it wasn't Louisiana; it was actually Gulfport MS. The item was in the 1940 meeting minutes, which can be found in the AASHTO database, but I have added the relevant text to this page (https://www.usends.com/west-memphis.html).