Established in 1960 as a renumbering of SC 77; little has changed since.
Two predecessors existed before the current SC 177 came to existence. The first appeared from 1930-1936 as a new primary routing from US 176/SC 10, in Spartanburg, to the North Carolina state line; it eventually became part of SC 9. The second appeared from 1938-1951 as a new primary routing from US 176, southeast of Pomaria, to US 76/SC 2, near Ballentine. It was adjusted twice, in 1948 extending and replacing SC 664, and in 1950 shifting to meet with US 176/SC 121 split. It was eventually renumbered as an extenstion of US 176.
South Carolina Highway 77 (SC 77) was established in 1937 as a renumbering of SC 98, from Wallace to the North Carolina state line. In 1960, this became SC 177.
Another SC 77 reappeared only appeared on South Carolina official maps in 1981-1982 as a proposed segment of I-77, from US 76/US 378 to I-20. When the freeway eventually opened, it was simply labeled as I-77.