Assumption Parish was established in 1834 and included the communities from Portugal Cove South to St. Vincents. However, Assumption Parish was divided twice. When Holy Redeemer Parish was established (ca. 1845), Portugal Cove South, Trepassey and St. Shotts were separated from Assumption Parish. In 1923, the communities of Peter's River, St. Stephen's, and St. Vincent's were removed from Assumption Parish to create Sacred Heart Parish. Assumption Parish currently includes the communities of Riverhead, Mall Bay, Coot's Pond, Path End, St. Mary's, Point La Haye and Gaskiers, with the parish church at St. Mary's.
The first parish priest assigned to Assumption Parish was Rev. James Duffy. However, priests visited St. Mary's prior to Father Duffy's arrival. Rev. Timothy Browne, for instance, who was stationed at Renews, performed 13 marriages at St. Mary's in 1825 and 1826.
By 1840 Rev. Duffy had established a church and school in St. Mary's; this church was dismantled in 1949 and rebuilt by 1950. Aside from the original school established by Rev. Duffy, a commercial school was opened in 1851. With the arrival of the Presentation Sisters to the parish in 1859, a convent school was established at St. Mary's.
Some of the communities in Assumption Parish also had their own church and school, including Riverhead and Mall Bay, which had a small chapel built sometime between 1895 and 1905 (replaced ca. 1963). Schools were also established in Mall Bay (1944), at the Gulch, Point La Haye (1943) and Gaskiers and Point La Haye (1951).
Parochial organizations in Assumption Parish included the Crusaders of Mary, the Children of Mary, the St. Anne Society and the Holy Name Society.