US 220 ALT #1: In April 1954 (CTB), US 220 was given a split routing. The new split was not given primary mileage but followed US 11 away from US 220 in downtown Roanoke, then headed off from US 11 on 1st St south to Franklin down to Maple. Though not mentioned in CTB minutes or on any maps I can find, it was signed in the field as US 220 ALT. I do not know if it was signed northbound as both places I have seen WSTS footage are in the Southbound direction.
I presume US 220 ALT went away in 1974 when US 220 was moved onto I-581 and US 220 Business was signed through downtown.

US 220 ALT #2: Appears in several CTB Minutes from 1958-61 describing construction of the Rocky Mount bypass.
When the bypass opened in 1961 it was designated as mainline US 220. Official maps through most of the 1960s showed it erroneously as US 220 ALT anyway.

US 220 ALT splitting from US 11 WSTS Screenshot, Sept 1960

US 220 bypasses Rocky Mount (US 220 ALT designation in error by this time) 1963 Official