In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Bagillt like this:
BAGILLT, a village, a township, and a chapelry in Holywell parish, Flint. The village stands on the S side of the estuary of the Dee, contiguous to the Chester and Holyhead railway, 2 miles NW of Flint, and 2¼ SE of Holywell. It has a station on the railway, and a post office‡ under Holywell; and is a sub-port to Chester. ...
The tract round it is rich in minerals, and yields a great output of coals; and the village itself is the seat or centre of extensive lead, iron, and alkali works. So large a quantity of lead ore as 100,000 tons, accompanied by 42,000 ounces of silver, has been annually smelted. One of the adjacent hills bears the name of Bryn-Dychwelwch, signifying "the hill of retreat;" and was the place at which Owen Gwynedd sounded his retreat from the pursuit by Henry II. Bagillt Hall, in the vicinity, is an old seat of the Griffiths.-The township bears the name of Ba gillt-Fawr, and includes the hamlets of Bagillt-Bach and Bagillt-Fechan. Real property, £7,040; of which £927 are in mines.The chapelry was constituted in 1844. Pop., 2,935. Houses, 687. The living is a p. curacy in the diocese of St. Asaph. Value, £155.* Patron, the Vicar of Holywell. The church is in the early English style, and was opened in 1839. There are chapels for Independents, Baptists, Wesleyans, and Welsh Methodists.
GB Historical GIS / University of Portsmouth, History of Bagillt in Flintshire | Map and description, A Vision of Britain through Time.
Date accessed: 23rd March 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 " Bagillt ".