The oldest known church in the parish of Mullagh was the Catholic Church, Teampall Cheallaigh “the Church of Ceallach,” the original Gaelic form of the name Kilian. It is situated close to the Mullagh town on the rise above the lake, adjacent to the present Church of Ireland. The ruins which still stand in the churchyard are reputed to be that of the old church and suggest a small building with rectangular windows, apparently finished with plaster, a fire place and a chimney.
Teampall Cheallaigh served as parish church during the time of the O’Reilly Clan; it was under their patronage and was the burial place of its members.
The old graveyard of Teampall Cheallaigh dates back to pre-Reformation times-circa 14th century. Exploration of these historic grounds takes one back through the past centuries as the site has been used as a burial place of our ancestors. The oldest gravestone is that of Philip O’Reilly who died on February 1st 1683. The names of many other local families can also be traced through the centuries – McCabe, O’Farrelly, McGowan, Doughty. (Portrait of a Parish. 1988)