John Myles was born in Wales around 1621 and was educated at Brasenose College at Oxford University.
After the restoration of the monarchy and requirement for all ministers to adhere to the Book of Common Prayer, Myles left England for the Plymouth Colony in the 1660s.
Myles took the historic Ilston Book to North America with him, and it is now located at Brown University in Providence, Rhode Island.
In America Myles worked with the Congregationalist state church in Rehoboth before his group was told to leave the town for its Baptist views, and Myles and his congregation (largely from Ilston, Wales) then founded the town of Swansea and First Baptist Church in Swansea.
During King Philip's War, Myles pastored the First Baptist Church in Boston while fleeing from the Indians.