This site uses Google maps which already has the location of some currently open pub sites already marked.

Early maps were not always accurate and rarely marked inns because most were in towns (and there wasn’t room to indicate them all). Pubs were not marked because they didn’t normally provide accommodation but some were marked if they were isolated (and therefore of great value to those who were unable to proceed to the next town).

Early maps
Most of the early maps of Ceredigion from the 17th century to the early 20th century (except for estate maps) have been searched for references to pubs, and relevant parts have been uploaded onto this web site and linked to the records for pubs (but it is possible that not all marked pubs have been found.)
The absence of an inn, pub or beer house on a map is no indication of whether it was open or closed at the time the map was surveyed or re-surveyed.

Tithe maps and apportionments.
During the 19th century, the annual tithes (10ths) of produce due to the church by every farmer were gradually commuted to cash payments. This was calculated mostly in the 1840s when detailed maps of every field were produced and lists of every occupier and owner of all productive land were compiled. Pubs sometimes appear on these maps, but if they consisted only of a building and garden, they were not liable to pay tithes. Most town property was also excluded from tithe payments.
All the surviving parish tithe maps for Wales have been scanned. It is possible to view the maps, which have been digitally reshaped to conform to modern maps, and view them either side-by-side with a modern 1:10,000 (6 inch) map or view them as an overlays, with the option of making one or other map more visible.
A few parishes have earlier tithe maps and lists, e.g.
Admeasurments and Valuation of the Parishes of Llanarth and Llanilar in the County of Cardigan. The Tithes of which belong to the See of St David. By William Couling, Brecon, 1814 and 1815, Ceredigion Archives, AXD/32, (with accompanying maps ADX176 [also by William Couling], 1814-1816.

Ordnance Survey maps
The Ordnance Survey maps did not mark every inn, pub (marked P.H. on Ordnance Survey maps) or Beer Houses (B.H.), especially in urban areas, but they did mark and name many in rural areas, especially on the large scale maps (1:2,500 (25 inch); the 1:500 (50 inch) scale maps exist only for Aberystwyth).
In some cases, where two adjacent pubs are known to have been open when the map was prepared, one is marked and named, and the other is indicated simply has ‘Inn’ or ‘P.H.’ or not at all. It is not known what criteria the Ordnance Survey used to distinguish between these, and other categories of licenced premises.

The following maps have been searched for pubs and inns. Hard copies are in the NLW and Ceredigion Archives (the sets of the larger scale maps are incomplete).
6 inch (late 1880s -1890s)
6 inch (early 20th century)
25 inch (late 1880s -1890s)
25 inch (early 20th century)
50 inch (1880s and 1905), Aberystwyth only

Many interactive maps are now available on line including early editions of Ordnance Survey maps.
Old Maps
Cymru 1900
National Library of Scotland