The introduction of the letter is straightforward– “James, a servant of God and of the Lord Jesus Christ, To the twelve tribes in the Dispersion: Greetings. ” Who is this James, however?
There are three James’ mentioned in the New Testament:
1)James the Lesser (the son of Alpheus)
2)James the Greater (the son of Zebedee and the brother of John)
3)James the leader of the Jerusalem church (the brother of Jesus)
Here’s an article on James from the Oxford Dictionary of the Christian Church:
James, St, ‘the Lord’s brother’ (Mk. 6:3 and parallels). The natural interpretation of the NT evidence would imply that he was the son of the BVM [Blessed Virgin Mary] and St *Joseph, but for other possibilities see BRETHREN OF THE LORD. From 1 Cor. 15:7 it appears that he was granted a special appearance of the Lord after the Resurrection. From an early date he was, with St *Peter, a leader of the Church at Jerusalem (e.g. Gal. 1:19), and from the time when Peter left Jerusalem after Herod’s attempt to kill him (Acts 12), James appears as the principal authority, who presided at the council of Jerusalem recorded in Acts 15. Acc. to *Clement of Alexandria, as reported by *Eusebius (HE 2. 1), he was chosen ‘bishop of Jerusalem’. On the basis of Gal. 1:19 it has been argued that he was an Apostle, and he has been identified with the son of Alphaeus (see JAMES THE LESS); both Clement and *Hegesippus describe him as ‘James the Just’. Acc. to Hegesippus (ap. Eusebius, HE 2. 23) he was put to death by the Sanhedrin in AD 62. Among Jewish Christians he was held in high repute, and elaborate stories of his sanctity are reported by Hegesippus. The (fictitious) ‘Clementine Homilies’ and ‘Recognitions’, prob. 3rd-cent. Judaistic writings, purport to be addressed to him, while the apocryphal Infancy Gospel known as the ‘Book of James’ is ascribed to him, as is also the Gnostic ‘Apocryphal Epistle of James’ (qq.v.). Feast day in E., 23 Oct.; also in the American BCP (1979).