1920s The roadway that would eventually become the current SR 300 was established in 1920 as SR 3 from Thomasville to Albany, via Camilla. By October 1926, nearly all of the aforementioned route was paved. By October 1929, SR 3 was extended southwest to where US 319 currently crosses the state line. US 19 was designated along this route to Thomasville, and then its current route from Thomasville to Albany.
SR 35 was designated along a portion of highway that is the current route of US 19 from the Florida state line to Thomasville.
1930s By 1935, nearly all of the northern half of the section of SR 35 between the Florida state line and Thomasville was paved. Prior to the beginning of 1936, nearly all of that section of SR 35 was paved. By July, the rest of that section was paved. In March 1937, the section of SR 300 that currently travels from Albany to Cordele was established as a northern extension of
SR 133. By October the routings of the portions of US 19 southwest of Thomasville was shifted to its current routing, while SR 3 stayed on its original routing. The following August, a small portion of SR 133 southwest of Cordele was paved.
1940s By 1944, a very brief section of SR 133 northeast of Albany was paved. In early 1946, approximately half of the length of SR 133 between Warwick and Cordele was paved. In early 1948, all of SR 133 was redesignated as
SR 257. The section of SR 257 from Albany to the intersection with
SR 32 and the section from
Lake Blackshear to Cordele were paved. In 1950, nearly all of SR 257 was paved.
1950s to 1980s By 1952, the entire roadway that would eventually become SR 300 was paved. A section of the highway from Albany to Cordele was proposed as
Interstate 175 and then cancelled, but in early 1982, the
Georgia–Florida Parkway was approved to be designated along the entire stretch of what is now SR 300. By the next year, all of SR 257 was redesignated as SR 300 and the designation was applied to the rest of its current route. Later that year, the routings of SR 3 and SR 35 south of Thomasville were swapped. ==Major intersections==