The 14th Century pocket book, The Laws of Hywel Dda, was bought at auction by the National Library of Wales, Aberystwyth, for £541,250 earlier this month.
It is believed the book was taken to America by Welsh settlers in the 1700s.
The manuscript will be exhibited at the at the National Library's Hengwrt Room.
It was sold by the Massachusetts Historical Society of Boston.
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See also National Library of Wales purchases Laws of Hywel Dda manuscript for £541,250