In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Newmarket like this:
NEWMARKET, a village and a parish in Holywell district, Flint. The village stands near Offa's dyke, 3 miles S E of Prestatyn r. station, and 7 N W of Holywell; was once a market town; is a seat of petty sessions; and has a post-office under Rhyl, and fairs on the last Saturday of April, the third Saturday of July, the fourth Saturday of Oct., and the second Saturday of Dec. ...
The parish includes the townships of Gop and Graig, and comprises 1,031 acres. Real property, £1, 911. Pop.in 1851, 642; in 1861, 520. Houses, 121. The decrease of pop. was caused by emigration. The property is chiefly in one estate. Golden Grove is the seat of Col. Morgan. A very large tumulus, covering more than an acre, is at Gop; and is said to have been erected by the conquerors of the Ordovices. A carved pillar is at Maen-Achwynfan; and many barrows are on the heights. The living is a p. curacy in the diocese of St. Asaph. Value, £90. Patron, the Bishop of St. Asaph. The church is tolerable; and the churchyard contains a richly ornamented cross of the 14th century. There is an Independent chapel.
GB Historical GIS / University of Portsmouth, History of Newmarket in Flintshire | Map and description, A Vision of Britain through Time.
Date accessed: 23rd April 2017
Click here for more detailed advice on finding places within A Vision of Britain through Time , and maybe some references to other places called " Newmarket ".