The Apostle Paul probably wrote this letter cir. A.D. 48. It is thought to be the first or second written book of the New Testament. James was written about the same time frame and might have preceded Galatians.
Ancient Galatia was an area in the highlands of central Anatolia in modern Turkey. Galatia was bounded on the north by Bithynia and Paphlagonia, on the east by Pontus, on the south by Lycaonia and Cappadocia, and on the west by the remainder of Phrygia, the eastern part of which the Gauls had invaded. The modern capital of Turkey, Ankara lies in ancient Galatia. Galatia was named for the immigrant Gauls from Thrace, modern day Bulgaria, who became its ruling caste in the 3rd century BC. They were an intermixture of Gauls and Greeks. The Gauls were a Celtic people who also became the Scots, the Welch and the French.