To connect the diocesan faithful with Catholic Centennial Week Bishop M.F. Fallon chose to celebrate 300 years (the tercentenary) since the first Catholic Mass in southwestern Ontario.
One of the earliest French missionaries to come to southwestern Ontario to minister to the First Nations peoples was Joseph de La Roche Daillon, a Franciscan Recollect priest. Daillon visited the Neutral peoples and celebrated Mass with them near the Grand River. Today, the parish of St. Cecila in Port Dover continues to commemorate this site with an annual celebration and it is known by the parishioners as the Wintering Site.

