It connects the Florida state line, south-southeast of Folkston with the North Carolina state line, in Dillard, via Folkston, Blackshear, Baxley, Vidalia, Soperton Wrightsville, Sandersville, Greensboro, Athens, Demorest, and Clayton.

It also used to travel from Athens, through Arcade and Jefferson, to Commerce, which is now the route of SR 15 Alt.

After that, the two state routes continue to stay together, heading north through the community of Bristol.

The two state routes continue north to Wrightsville, where SR 78 departs eastward.

The highways then have an interchange with I-85, and head between the towns of Baldwin and Cornelia, where they become a limited access freeway for a short time and rejoin US 23.

The three highways remain together and head through the cities of Tallulah Falls, Clayton, and Dillard before crossing into North Carolina.

[2][3] By October 1926, US 1 was designated on SR 15 from the Florida state line to north-northeast of Alma.

[3][4] By October 1929, SR 4 was designated on US 1/SR 15 from the Florida state line to north-northeast of Alma.

This segment, as well as a portion south of Sandersville, had a completed hard surface.

[4][5] By the middle of 1930, the southern terminus was truncated to the point it previously left the concurrency with US 1/SR 4 north-northeast of Alma.

From just north of the Appling–Jeff Davis county line to Hazlehurst, SR 15 had a completed hard surface.

[20][21] By the end of the year, the Treutlen County portion of the Vidalia–Soperton segment of SR 29 was also completed.

[21][22] In the first quarter of 1937, SR 78 was established from Soperton north to Adrian and north-northwest to Wrightsville.

[40][41] Between July 1957 and June 1960, SR 15 was re-extended to the Florida state line, on its current path, to Wrightsville.

US 23/US 441/SR 15 between Tallulah Falls and a point about halfway between Clayton and Mountain City was shifted eastward; at this time, SR 343 was decommissioned.

[48][49] In 1976, SR 72 was indicated to be "projected mileage" from this point south to US 78/SR 10, then southwest and west to end at US 441/SR 15.

[52][53] The next year, the portion of the Athens freeway between US 29/SR 8/SR 72 and US 78/SR 10 on the northeastern part was downgraded to a divided highway.

was designated on the freeway from the then-current southern terminus to their current respective interchanges.

SR 72's western terminus was truncated to the far northeastern part of the city, at its current location.

[56][57] In 1986, a western cut-off, designated as SR 773, was proposed on a more direct path between two intersections with US 23/US 441/SR 15 from south of Tallulah Falls and into the city.

[62][63] The next year, a slightly western rerouting of US 129/US 441/SR 15 in the southern part of Athens, designated as SR 901, was proposed from US 129/US 441/SR 15 southwest of their southern interchange with the Athens freeway north-northwest to Timothy Road just north of the freeway.

This street features stately homes and mansions, some of which house college fraternities and sororities.

In Commerce, it split off of US 441 temporarily to the northeast and curved to the north-northwest to rejoin it at the spot where SR 98 also joined it.

[81][82] In 1972, it was redesignated as SR 15 Conn.[49][83] In 1981, the path of US 441/SR 15 in Baldwin was shifted westward, replacing the connector route.

was an alternate route of SR 15 that existed entirely within the city limits of Cornelia.

[44][45] In 1972, this highway was redesignated as SR 105 Conn.[49][83] The entire route was in Cornelia, Habersham County.

It is known locally as Level Grove Road, and is designed to facilitate northbound to southbound traffic between US 441/SR 15 and US 23/SR 365 (Tommy Irvin Parkway).

The roadway that would eventually become SR 15 Spur was established between January and September 1938 as an unnumbered road between two intersections with US 23/SR 15.

The loop travels to the east and curves to the northeast to a turnoff that leads to Tallulah Lodge.

At the Tallulah Point Overlook, it begins heading west-northwest and reaches its northern terminus, a second intersection with US 23/US 441/SR 15.