These altars, unmarked on early Ordnance Survey maps from 1834, were first officially documented during the OS revision of 1848. According to local historian J. Byrne, noted in the OS Revision Name Book, these were ‘old Roman Catholic altars’ specifically used for celebrating Mass when such practices were forbidden by law.

During the 17th and 18th centuries, Ireland’s Penal Laws severely restricted Catholic worship, forcing priests and congregations to gather in secret at remote outdoor locations known as Mass rocks or penal Mass stations. The six altars at Muff represent one such station, where local Catholics would have risked prosecution to practice their faith. These rough stone structures, weathered by centuries of Donegal rain and wind, would have seen priests arrive under cover of darkness or fog, with lookouts posted to warn of approaching authorities.

The site’s late appearance on official maps speaks to its secretive nature; for over a century after the Penal Laws were relaxed, these altars remained known primarily through local memory and oral tradition. Today, they stand as tangible reminders of a time when religious freedom couldn’t be taken for granted, their worn surfaces bearing witness to the determination of communities who refused to abandon their beliefs despite the considerable risks involved.