All Mikados used by the Georgia Railroad were designated class F63, what stood for their driver diameter of 63 (or 63.5) inches. The first batch was designed in World War I for the 171 miles between Augusta and Atlanta. A large part of this line consisted of short grades with up to 0.7 percent and had many curves. The new locomotives to be built had to have nearly twice as much power as the ten-wheelers then in use. The basis of these was the Harriman Common Standard Mikado. In 1915, Lima delivered numbers 300 to 302. Number 303 followed in 1918. Later two received thermic syphons and the other two received security circulators.

Seven more were also ordered from Lima in the twenties. These were based on the USRA Light Mikado, and compared to the older ones they had a smaller boiler with a higher pressure and a larger firebox. Compared to the standard USRA design, the superheater had been made larger. No. 320 to 324 were built in 1923, followed by 325 and 326 in 1925. Similar to the older ones, some later also got security circulators.

They were retired between 1952 and 1954 and all but 302 were subsequently scrapped. 302 was donated to the city of Augusta and is on display in the local museum. Six other locomotives which were also designated F63 had been bought from other railroads. 305 and 306 had been built by ALCO in 1907 for the Cleveland, Cincinnati, Chicago & St. Louis Railway and were sold to the Georgia Railroad in 1937. 331 to 334 were built by Baldwin in 1919 for the Clinchfield Railroad and came to the Georgia Railroad in 1943.