Note- in older civil registration and census records, the village and parish are usually described as "Newmarket".
When Civil Registration was introduced (on 1 July 1837), the parish of Trelawnyd was assigned to the No. 1 ("Whitford") sub-district of the Holywell Registration District, which was co-extensive with the Holywell poor law Union.
In the GRO indexes to civil registration, entries for Trelawnyd are found under:
- Years 1837 - 1851: Holywell XXVII. nnn
- Years 1852 - 1946: Holywell 11b. nnn
(GRO index references have no relevance at the local Superintendent Registrar's Office)