! Corthinthians was written by Paul while he was in Ephesus during his third missionary journey near the end of his stay in Ephesus in the year A.D. 55..

Sources:
Encountering the New Testament, Walter A. Elwell / Robert W. Yarbrough, 1998, Baker Books, page 290

A Survey of the New Testament, Third Edition, Robert H. Gundry, 1994, A Survey of the New Testament, Third Edition, Robert H. Gundry, 1994, Zondervan, page 360