1920s SR 15 was established at least as early as 1919 on three segments. The southern segment extended from the current southern terminus through Folkston, Waycross, and Alma, and ended at Hazlehurst. The central segment extended from SR 27 in
Lumber City to SR 19/SR 30 west-southwest of
Mount Vernon. The northern segment extended from SR 30 in Mount Vernon to Athens, through Jefferson to its current northern terminus. There was no indication if SR 15 traveled between the separate segments, though. By the end of September 1921, the portion of SR 15 from west-southwest of Mount Vernon to Wrightsville was shifted westward, to travel north-northwest to
Dublin and had a separate segment from SR 26 east-northeast of Dublin to Wrightsville (again no indication of SR 15 between the two segments). Its former path from Mount Vernon to Adrian was redesignated as part of SR 56. By October 1926, US 1 was designated on SR 15 from the Florida state line to north-northeast of Alma. US 129 was designated on SR 15 from just south of Watkinsville to Jefferson. Three segments had a "completed hard surface": a portion southwest of Waycross, a portion in the south-southwest part of Athens, and the Cornelia–Clarkesville segment. 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.
1930s 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. Four segments had a completed hard surface: a portion in the northwestern part of Athens, from southeast of Jefferson to southwest of Commerce, the Baldwin–Cornelia segment, and the Clarkesville–North Carolina segment. Between November 1930 and the beginning of 1932, US 23 was designated on the Baldwin–North Carolina segment. In January 1932, SR 29 was established on SR 15's current path from US 1/SR 4 in South Thompson through Vidalia to SR 56 in Soperton. In March, the Watkinsville–Athens segment was completed. The next month, SR 24 was extended from Athens to Commerce, on what is now SR 15's. Also, the Tennille–Sandersville segment was also completed. Nearly two years later, SR 121 was established from US 84/
SR 50 in Hoboken to SR 38 in Blackshear. Later that year, the southern terminus of the northern segment of SR 15 was shifted west-southwest to
Dublin, to connect with its central segment. From just north of the Appling–Jeff Davis county line to Hazlehurst, SR 15 had a completed hard surface. About one year later, the Johnson County portion of the Dublin–Wrightsville segment was completed. During the first half of 1936, two segments of SR 15 were completed: the Laurens County portion of the Dublin–Wrightsville segment and a short portion south-southeast of Baldwin. Later that year, the northern half of the Homer–Baldwin segment was completed. By the end of the year, the Treutlen County portion of the Vidalia–Soperton segment of SR 29 was also completed. In the first quarter of 1937, SR 78 was established from Soperton north to
Adrian and north-northwest to Wrightsville. In the third quarter of the year, three segments of SR 15 were completed: the entire southern segment (from north of Alma to Hazlehurst), a portion north-northeast of Lumber City, and from the Hancock–Greene county line to just north-northwest of Greensboro. The next year, SR 121 was extended southward to US 1/SR 4 in Racepond and northward to Baxley. Two segments of SR 15 were completed: the Athens–Jefferson and Homer–Baldwin segments. By July 1939, the Vidalia–Soperton segment, as well as a portion in the southeastern part of Commerce, of SR 29, and a portion in the southern part of Wrightsville on SR 78, was completed. Later that year, the entire Commerce–Homer segment of SR 15, as well as the northern half of the South Thompson–Vidalia segment of SR 29, was completed. By the end of the year, all of SR 15 north of Watkinsville, as well as a portion of SR 24 in the extreme northern part of Athens, was completed.
1940s In 1940, the Wrightsville–Tennille segment of SR 15, as well as the portion of SR 78 from Soperton to north-northwest of Adrian, was completed. In the second half of 1941, the Adrian–Wrightsville segment of SR 78 was completed. The next year, a portion of SR 15 southeast of Sparta, as well as the southern half of the South Thompson–Vidalia segment of SR 29, was completed. Between January 1945 and November 1946, US 319 was designated on the Dublin–Wrightsville segment of SR 15. Three segments of SR 15 and one segment of SR 24 were "hard surfaced": from Lumber City to north of
Glenwood, from Sandersville to just south of Warthen, the Sparta–Greensboro segment, and the Jackson County portion of SR 24. By February 1948, the Sandersville–Sparta segment of SR 15, the Pierce County portion of the Hoboken–Blackshear segment of SR 121, a portion of SR 121 south-southeast of Baxley, and the entire Athens–Commerce segment of SR 24 were all hard surfaced. By April 1949, US 441 was designated on the Watkinsville–Athens and Commerce–Baldwin segments of SR 15 and the Athens–Commerce segment of SR 24. Two segments of SR 15 were hard surfaced: a portion south-southeast of Dublin and the Oconee County portion of the Greensboro–Watkinsville segment.
1950s and 1960s By August 1950, US 23 was designated on US 1/SR 4 from the Florida state line to north of Alma and on the southern segment of SR 15 from north of Alma to Hazlehurst. The Wheeler County portion of SR 15 and the Greene County portion of its Greensboro–Watkinsville segment, as well as the Blackshear–Bristol segment of SR 121, was hard surfaced. By the beginning of 1952, US 441 was designated on US 23/SR 15 from Baldwin to the North Carolina state line. The Glenwood–Dublin segment of SR 15 and the Racepond–Hoboken and Bristol–Baxley segments of SR 121 were hard surfaced. Between July 1957 and June 1960, SR 15 was re-extended to the Florida state line, on its current path, to Wrightsville. Its former path from north of Alma to Dublin was redesignated as
SR 19; its former path from Dublin to Wrightsville, on US 319, was redesignated as SR 31. The paths of SR 15 and SR 24 between Athens and Commerce were swapped. By June 1963,
SR 350 was established from US 129/SR 15 in the northwestern part of Athens to US 29/SR 8 in the northeastern part of the city. SR 15 and SR 24 between Athens and Commerce were swapped back. The path of SR 15 between Tallulah Falls and
Tiger was shifted southwest on a more direct path. Its former path on US 23/US 441 was redesignated as
SR 343. By the beginning of 1966, SR 24's northern terminus was truncated to Watkinsville. SR 15 replaced the Watkinsville–Athens segment, and
SR 15 Alt. replaced the Athens–Commerce segment. US 29 was designated on SR 350 from the US 129/SR 15 interchange, which also had
US 29 Temp. and
US 441 Temp., to the US 29/SR 8 interchange. US 441 Temp. was designated on it from the US 129/SR 15 interchange to the US 441/SR 15 Alt. interchange. A western extension of SR 350, ending at US 29/US 78/SR 8/SR 10, was under construction. Also, SR 350 was under construction east-southeast just slightly from the US 29/SR 8 interchange. 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. In 1966, SR 350 was decommissioned. US 29 was designated on the freeway from the western terminus to where it, as well as SR 8, depart the freeway. This interchange also had
SR 8 Bus. and
SR 106. SR 8 was designated on the entire length of the freeway. Its former path through the city was redesignated as SR 8 Bus., still concurrent with US 78/SR 10. In 1967, US 29 was extended on the freeway one interchange to the east. At this interchange,
SR 72 was extended southeast to end here, concurrent with US 29/SR 8.
1970s and 1980s In 1971, the path of US 23/US 441/SR 15 in the Baldwin–Demorest area was shifted westward. Their former path became
US 23 Bus./
US 441 Bus./
SR 15 Loop. 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. In 1980, the Athens freeway was completed along its proposed extension's path, with US 129/US 441/SR 15 designated on it. The path of SR 15 in the Clarkesville area was shifted eastward, off of US 23/US 441 and partially onto
SR 115. 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. In 1983, US 129/US 441/SR 15 Alt. was designated on the freeway from the then-current southern terminus to their current respective interchanges. In 1985, US 441 Temp. was no longer shown on maps. SR 72's western terminus was truncated to the far northeastern part of the city, at its current location. 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. The next year, SR 10 was designated on the Athens freeway from the US 129/US 441/SR 15 to the eastern US 78/SR 10 Bus. interchange. Its old path through downtown, still concurrent with US 78, was redesignated as SR 10 Bus. At this time, SR 72 was re-extended to the northeastern interchange. The path of US 23/US 441/SR 15 in the Tallulah Falls area was shifted westward, onto the proposed path of SR 773. The former path was redesignated as
SR 15 Loop. In 1988, SR 10 in Athens was shifted back to downtown, with SR 10 Loop designated on the city's freeway. US 78 was shifted to the southern side of the freeway, with its former path redesignated as US 78 Bus. A southern
bypass of Demorest and Clarkesville, designated as a northern extension of SR 365, was proposed from SR 365's then-current northern terminus at US 23/US 441/SR 15 south-southeast of Demorest to SR 115 south-southeast of Hollywood. At this time,
SR 365 Spur was proposed from SR 115 at SR 365's proposed extension north-northwest to Hollywood. The next year, an eastern bypass of the main part of Commerce, designated as
SR 759, was proposed from US 441/SR 15 south-southeast of Commerce to another intersection north-northeast of the city. SR 365 extended east-northeast on its previously proposed path to SR 115 south-southeast of Hollywood. An eastern bypass of Hollywood and
Turnerville, designated as
SR 835, was proposed from SR 17 just south of Hollywood to US 23/US 441/SR 15 south-southwest of Tallulah Falls.
1990s and 2000s In 1991, the paths of SR 15 and SR 15 Alt. between Athens and Commerce were swapped. SR 759 around Commerce was completed. An eastern bypass of Homer, designated as
SR 765, was proposed from US 441/SR 15/SR 164 south-southeast of Homer to US 441/SR 15 north-northeast of the city. Also, the path of US 23/SR 15 in the Demorest–Hollywood area was shifted off of US 441 and onto SR 365 from south-southeast of Demorest to south-southeast of Hollywood, then north-northwest on the proposed path of SR 365 Spur to Hollywood. 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. The path of US 441/SR 15 in the Commerce area was shifted eastward, replacing SR 759. The former path of US 441, on SR 334 and SR 98, was redesignated on
US 441 Bus. A southeastern bypass of
Hollingsworth, designated as
SR 876, was proposed from US 441/SR 15 south-southeast of Hollingsworth to SR 198 southeast of the community. A cutoff, north-northeast of Hollingsworth, was proposed as an unnumbered road from Hollingsworth to US 441/SR 15 north-northwest of it. The path of US 441, from south-southeast of Demorest to Hollywood, was shifted southeast, onto the path of US 23/US 441/SR 15/SR 365. The former path of US 441 was redesignated as a northern extension of US 441 Bus. In 1993, the path of US 23/US 441/SR 15, from Hollywood to Tallulah Falls, was shifted eastward, onto the proposed path of SR 835. The next year, the cutoff north-northeast of Hollingsworth, now proposed as
SR 877, was extended to SR 105 just east of the southern end of US 441/SR 15 concurrency. In 1995, US 29/SR 8 was also shifted to the southern side of the freeway, concurrent with US 78/SR 316. SR 72's western terminus was once again truncated to its current location. In 1997, the path of US 441/SR 15, from Homer–Cornelia, was shifted eastward, onto the proposed path of SR 876. In 2001, the path of US 129/US 441/SR 15 in Athens was shifted westward, onto the proposed path of SR 901. They were placed on a southern concurrency with the freeway for less than . This brief concurrency ended at Macon Highway. The next year, US 129/US 441/SR 15 was shifted off of Macon Highway and onto the Athens freeway. SR 877 was canceled. Two years later, the unsigned SR 422 designation was applied to the Athens freeway. The path of US 441/SR 15 in Homer area was shifted eastward, onto the proposed path of SR 765. ==Major intersections==