"Mostyn .... of late years has become a place of great importance. A steam packet plies between this place and Liverpool, which affords accommodation for the conveyance to and fro of a vast number of persons and a great quantity of goods, and that at a most reasonable rate. It is computed that no less than about 250,000 tons of coals are produced from the different pits in this neighbourhood annually. .... There is also a large foundry in this place, where steam-engines of every description are manufactured." [From A Visitor's Guide to Rhyl and its Vicinity, D. Lloyd Lewis, 1852].
The new parish of Mostyn was created by an Order in Council, on 23 May 1844, from the townships of Bychton, Mertyn Isglan, and part of Trefostyn, all of which had been in the parish of Whitford until that date.
The Order in Council, which appeared in the London Gazette of 3 June 1844, defined the boundaries of the new parish of Mostyn as follows:.
"All that part of the Parish of Whitford, bounded on the N.E. by the estuary of the Dee, on the S.E. by the Parish of Holywell, and on the S.W. and N.W. by an imaginary line, commencing at a point on the N.W. bank of Aber Oswald brook, opposite to the southern corner of a certain mill belonging to Mr. Foulkes, and thence extending toward the N.W. along the S.W. side of such mill, and along the middle of a certain lane situate on the N.E. of Werglodd-y-felin, and the public footpath through the fields called respectively Wern Mablu, Werglodd y Plassau, and Werglodd Sion Pierce, as far as the middle of a certain lane leading by a certain farmhouse and premises called Mertyn Garnons, and thence extending northward along the middle of such last mentioned lane to a point opposite to the S.E. corner of the same farmhouse and premises and thence along the S.W. and N. sides of the same farmhouse and premises, and thence eastward in a straight direction as far as the middle of the last-mentioned lane, and thence northward, along the middle of the same lane as far as Mertyn Hugh Roberts' farmhouse, and thence towards the N.W. along the middle of a certain footpath through the fields called respectively Caeau-tan-ty, Caeau'r Doctor, Coetiaur Chwarel, and Clwt field, and thence in the same direction across a certain lane leading to Bryn-y-baw, and along the middle of another lane called Ffordd-y-Clwt to a point opposite the N.E. corner of a certain field called Cae Cengen, and thence westward along the N. side of such last-mentioned field, as far as a certain rivulet near a certain farmhouse called Mertyn Parry, and thence towards the N.W. along the middle of such rivulet as far as the middle of the turnpike road at Gwibnant, and thence in the same direction along the middle of such road as far as the middle of the turnpike road leading from Tre Mostyn, and thence towards the N.E. along the middle of such last-mentioned road as far as the turnpike gate adjoining the Park wall of the Hon. E.M.Ll. Mostyn, and thence partly in the same direction and partly towards the N.W. along such wall to the point where the same terminates, and thence towards the N.E. in a straight direction till it reaches the aforesaid Estuary or marsh."