SC 72 ALT #1: Appeared in 1942 as what was almost certainly a renumbering of SC 7 ALT, running as a wye between US 176 and SC 72 northeast of Whitmire.
In 1947, SC 72 ALT became US 176-SC 72 CONN.
SC 72 ALT #2: Appeared in 1950 as a renumbering of US 21 ALT on the southernmost part of the Rock Hill Bypass.
In 1953, SC 72 ALT was renumbered as mainline SC 72. Today it is SC 5.

SC 72 ALT near Whitmire 1943 Union County

US 21 ALT shown explicitly before it became SC 72 ALT 1948 City of Rock Hill