That's a link to citrus plant zones and citrus breeds for Georgia, in general, not oranges in particular. And it carefully notes zone A along the southeastern corner of the state is just about the only zone that citrus stands a chance. And they all carefully mention that you have to be very careful about providing freeze protection even with those specific breeds. There is no orange production at scale in Georgia.

It is interesting to note these statements from the above publication:

"History indicates that citrus plants have been grown for many years in gardens near the Gulf of Mexico and even as far north as Charleston, South Carolina. Small satsuma plantings were developed in the Gulf states as early as the 1890s but were destroyed by the freezes of 1894-95 and 1899. Plantings resumed until the freeze of 1916-17 struck, killing thousands of acres. By the early 1940s the hardy satsuma had again made a comeback, with some 12,000 acres growing in the Gulf states of Louisiana, Alabama and northern Florida. But freezes in the two decades following World War II mostly eliminated these plantings. Currently the main commercial areas are on the Gulf Coast of Louisiana and Florida."

Which seems to indicate that the climate was warmer than present in certain portions of the last few centuries. Charleston regularly experiences overnight freezes throughout Dec, Jan, and Feb (crucial months for orange production) in the modern era.