Sometimes called "the Proverbs of the New Testament," the book of James practically and faithfully reminds Christians how to live. From perseverance to true faith to controlling one's tongue, submitting to God's will, and having patience, this book aids readers in living authentically and wisely for Christ. Many have claimed that James and the apostle Paul differed on the question of faith versus works, but in reality the spiritual fruit that James talks about simply demonstrates the true faith of which Paul wrote. Their writings are complementary rather than contradictory. Possibly one of the earliest of the New Testament writings (a.d. 40-50), the book is believed to have been written by Jesus' brother James (Gal. 1:19).

There's textual reasons for both cases that depends on how one interprets Galatia.  South Galatian Theory treats Galatia as the whole Asian province while the North Galatian Theory treats Galatia as an isolated location. 

In the letter, Paul referenced that it has been 17 years (Gal 1:18 + 2:1) from his conversion on the Road to Damascus.  If one dates the crucifixion at 30 AD, Paul's conversion taking place 2 years after that one arrives at 49 AD for the composition of Galatians. 

A. Paul's Apostleship (Ch 1) 
B. Paul's Authority (Ch 2)

A. Slavery in the Law (Ch 3) 

B. Freedom in Grace (Ch 4)  

A. Christian Liberty (Ch 5) 

B. Christian Duties  (Ch 6)