The original SC 30 traveled from St. George to Beaufort. In 1926, SC 39 was extended north with SC 4 from Santee to Summerton on a new route to Sumter, replaced SC 42 north to Bishopville, east with SC 34 to Lydia, then replaced SC 351 north to Hartsville, then northeast on a new route through Society Hill to Bennettsville, then replaced SC 38 northeast to the North Carolina state line at McColl. In 1927, it was truncated to Walterboro, as parts were transferred to US 17 and SC 28 (this segment is now part of US 21). The remainder became part of US 401 in 1933.