The Galatians were in south-central Asia Minor, the turning around point of Paul's first missionary journey, including the cities of Iconium, Lystra, and Derbe. Actually, Derbe was only 125 miles from Paul's original home of Tarsus, on the main east-west Roman road, but there was a mountain range in between, and not much general intercourse.
The date of the epistle, and its time-position in relation to Paul's travels, is not certain, but it appears to be early, and some consider it his first epistle. It was certainly after his first visit to them (Acts 14), and seems to be before the Jerusalem council (Acts 15), though this is not certain. If it was, it would be during the "long time" at Antioch of Acts 14:28.
Bro Growcott - By Love Serve One Another