SC 73 ALT: Appeared in 1942 as a renumbering of SC 331 ALT from SC 28 (now US 278) along Marion St to Railroad Ave then west to SC 3-331 (now US 278-301) in Allendale.
In 1947, SC 73 ALT was downgraded to S-3-9 on Railroad Ave east of Main and S-3-10 west of Main. Today it is S-3-10 on Railroad Ave and S-3-14 on Marion St.
SC 73 ALT is explicitly mentioned in SC Highway Department Annual Reports of the mid 1940s.