The origins of the church of All Saints by-the-Sea go back well over a century. The Reverend John Thomas Magrath, an 1862 Bowdoin graduate, became the rector of Christ Church in Gardiner, Maine from 1866 to 1869. He then ministered to congregations in Michigan, Philadelphia, and Boston.

While in Gardiner, Magrath and members of his congregation came to Pig Island (now Capitol Island) on picnics. He noticed a green hayfield on the east shore of Southport, and his family acquired this small saltwater farm. They built a summer cottage on this land in the early 1870s. Since there was no Episcopal Church accessible to the vacationers, they established the congregation of All Saints by-the-Sea under the leadership of Magrath. Services were held under the oak trees surrounding the hayfield or in the cottage if the weather was foul. This original cottage is still owned by members of the Moses family.

In the 1870s, Mary Williamson, a member of the Gardiner congregation who had visited many time, purchased land to the south of the Magrath farm. She donated part of this land for the building of a church. The present church was erected on that land in 1905. The architect, Albert Hall, donated his services, and the construction was done by a neighbor, Charles Gray. The Right Reverend Robert Codman, Bishop of Maine, consecrated the All Saints by-the-Sea in July 1906.

Rev. Magrath continued to be in charge of the church until his death in 1908. Subsequently, clergy from all over the country have officiated at services each summer at the chapel on Southport.

While not a parish church in the ordinary sense, neither is All Saints by-the-Sea a Diocesan Mission. It remains essentially a congregation of residents and summer visitors who share its services and give it their support. Its island location and approach by water have endeared the church to many and have made it an important part of the region’s summer life. Over the years All Saints has become a spiritual summer home of hundreds of worshippers of all denominations in the Boothbay area.