Loca Patriciana: An Identification of Localities, Chiefly in Leinster, Visited by Saint Patrick and His Assistant Missionaries; and of Some Contemporary Kings and Chieftains; with an Essay on the Three Patricks, Palladius, Sen Patrick, and Patrick MacCalphurn, Apostles of Ireland in the Fifth Century

Published in 1879, Loca Patriciana represents a significant effort by the Reverend John Francis Shearman to systematize the fragmented hagiography and geography surrounding the mission of Saint Patrick in Ireland. Born from the mid-19th-century intellectual drive to reconcile oral traditions with early medieval annals, the volume focuses specifically on the Leinster region. Shearman sought to move beyond simple folklore by cross-referencing local site names with primary historical texts, intending to create a definitive topographical guide for scholars interested in the roots of Irish Christianity.

The most controversial and enduring aspect of the work is Shearman's thesis regarding the 'Three Patricks.' By proposing that the figure of Saint Patrick was a composite of three distinct missionaries—Palladius, Sen Patrick, and Patrick MacCalphurn—Shearman engaged in the rigorous, albeit contentious, historical criticism of his time. While later academic consensus has moved toward a more singular focus on the primary Patrician mission, the book remains a prized artifact for researchers of 19th-century Irish antiquarianism, illustrating the period's fervent dedication to reconciling mythological narratives with topographical reality.