The canons were established as part of the Canon at the Council of Hippo in A.D. 393 - Here is the canon from that council:
"It has been decided that besides the canonical Scriptures nothing be read in church under the name of divine Scripture.
But the canonical Scriptures are as follows: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua the Son of Nun, Judges, Ruth, the Kings, four books, the Chronicles, two books, Job, the Psalter, the five books of Solomon (included Wisdom and Ecclesiastes (Sirach)), the twelve books of the Prophets, Isaiah, Jeremiah, Daniel, Ezekiel, Tobit, Judith, Esther, Ezra, two books, Maccabees, two books."
This OT canon was then confirmed at the Council of Carthage in 397 A.D. Here is that Council Canon:
Council of Carthage III. "It has been decided that nothing except the canonical Scriptures should be read in the Church under the name of the divine Scriptures. But the canonical Scriptures are: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua, Judges, Ruth, four books of Kings, Paralipomenon, two books, Job, the Psalter of David, five books of Solomon (Proverbs, Ecclesiastes, Song of Songs, Wisdom, Sirach), twelve books of the Prophets, Isaiah, Jeremiah, Daniel, Ezekiel, Tobit, Judith, Esther, two books of Esdras, two books of the Maccabees."
These books are part of the oldest existing manuscript of the Bible, the Codex Vaticanus.