Its identification with the Kidron Valley, which began in the fourth century, is somewhat uncertain since no actual valley of this name is known to pre-Christian antiquity. Eusebius in the Onomasticon (ed. Klostermann, p. 70) located the valley of Jehoshaphat in the Valley of Hinnom, possibly because of the judgments that were associated with that place in connection with the idolatrous kings of Judah (cf. Jer. Jer. 7:31f; Jer. 19:5f, where it is called the valley of Slaughter). Since the time of the Pilgrim of Bordeaux (A.D. 333), however, the Kidron has become increasingly the site popularly accepted.4Others suggest the name is descriptive of what God will accomplish (judgment) at the location rather than any association with an event in the life of King Jehoshaphat. Perhaps it is to be associated with the plain of Esdraelon:
It is clear both from the contexts of Joel Joel 3:2, Joel 3:12 and from the term used twice in Joel Joel 3:14, the valley of decision (cf. Zep. Zep. 3:8), that the name is to be interpreted as the scene of judgment, and not taken from the king of the same name. Eze. Eze. 39:11 and Rev. Rev. 16:16+ seem to locate it in the plain of Esdraelon (Armageddon).5
2 Joel Joel 3:2, Joel 3:13 speaks of events taking place in the valley of Jehoshaphat, which seems to be an extended area east of Jerusalem.J. Dwight Pentecost, Things to Come: A Study in Biblical Eschatology (Grand Rapids, MI: Zondervan Publishing House, 1958), 341.