US 23-A was born about 2006 as a renumbering of mainline US 23 which was moved onto I-26 in northern Madison County. This is the 4th US 23-A.
US 23-A is erroneously shown on official maps as US 23 Business, but Google Streetview shows it is posted in the field as US 23-A.
I'm not sure the point of this remaining a US route. If it really is necessary to keep it as a primary route, why not an extension of NC 213 or a revival of NC 36?

US 23 not on I-26

US 23 becomes US 23-A

The 1st US 23-A was born when US 23 was given a new routing through Waynesville via today's US 276 and Walnut St. Main St then became US 19A-23A. This occurred between 1939-44.
US 23-A likely went away when US 23 bypassed Waynesville in 1968. Oddly, the 1968 Haywood County map shows the route as US 23-A Business.

US 19-23 on Main St. in Waynesville

US 19A-23A on Main St. in Waynesville

The 2nd US 23-A appeared about 1949 as a renumbering of mainline US 23 through West Asheville into downtown Asheville. It used Haywood through W. Asheville, then Clingman Ave to Patton Ave which was then-US 23.
US 23-A (100% duplex with US 19-A) was renumbered as US 23 Business in 1960. East of I-240 is no longer primary routing.

US 23 through W Asheville

US 23-A through W. Asheville

US 23-A becomes US 23 Bus

The 3rd US 23-A appeared about 1962 as a short connector between I-40 and US 19-23 in western Buncombe County. The '62 Official implies that today's US 74 between US 19-23 and I-40 west of Canton may have been part of this as well but the '62 and '68 Haywood County maps do not give a route number (primary or secondary) to this connector.
The segment of US 23-A that is explicitly labeled went away about 1971 when I-40 was extended east to Asheville. Today there is no evidence a road was ever in that location.

US 23-A implied on both ends of prop I-40

US 23-A in western Buncombe