In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Bryn Mawr like this:
BRYNMAWR, a large seat of iron-works, on the northern border of Monmouth; on the Merthyr and Abergavenny railway, in the vicinity of Nantyglo. It has a post office‡ under Tredegar, a r. station, an inn, a church, and several chapels. A railway from it to Blaenavon was authorised in 1866.
A Vision of Britain through Time includes a large library of local statistics for administrative units. For the best overall sense of how the area containing Bryn Mawr has changed, please see our redistricted information for the modern district of Blaenau Gwent. More detailed statistical data are available under Units and statistics, which includes both administrative units covering Bryn Mawr and units named after it.
GB Historical GIS / University of Portsmouth, History of Bryn Mawr, in Blaenau Gwent and Brecknockshire | Map and description, A Vision of Britain through Time.
Date accessed: 18th April 2015
Click here for more detailed advice on finding places within A Vision of Britain through Time, and maybe some references to other places called "Bryn Mawr".