The Ilston Book is the earliest record of a Baptist church in Wales. It is named after the location of a Baptist meeting place near the ruins of the old Trinity well, the site of a pre-Reformation chapel, at Ilston Beck in Gower near Swansea.
This "Cromwellian" church was founded in 1649 during the English Civil War under the Calvinistic leadership of John Myles (aka John Miles) (1621–1683). Thus this earliest Welsh Baptist church stood in the Particular Baptist tradition.
In 1663 Myles took the Ilston Book with him when he and the whole congregation emigrated to North America, where they settled in a town they named Swansea, Massachusetts, and they founded the First Baptist Church in Swansea.
The Ilston Book is held in the Library of Brown University[1] at Providence, Rhode Island, but is not open to public view.
The full list of 261 members up to 1660 is recorded, and shows that they travelled from a wide geographical area in South Wales.
Baptists in Early North America, Vol. 1, Swansea, MA, William Brackney with Charles Hartman; Mercer University Press, 2013