US 221-Y: Appeared 1942 as a renumbering of SC 110 ALT, running as a cutoff between US 221 and US 221 ALT/SC 11 east of Chesnee.
It is unclear when US 221-Y was renumbered as US 221 CONN. It is shown as US 221-Y on the 1950 Cherokee County map and then no map labels the cutoff explicitly again until 1978.

SC 110 ALT between SC 110 and US 221 1940 Cherokee County

SC 110 ALT becomes US 221-Y 1943 Cherokee County

US 221-Y becomes US 221 CONN 1978 Cherokee County