Church of the Most Holy Trinity, formally organized in 1810, is a monument to one of Georgia's earliest Catholic communities. The current building, constructed from 1857-1863, is the oldest surviving Catholic Church building in Georgia. The history of this community and its contributions both to Augusta's development and Georgia history are reflected in the building records of the present structure which was consecrated at the height of the Civil War. With the tower and some embellishments added in the late 19th and 20th centuries, the building is an impressive example of Romanesque Revival in 19th century church architecture.

The records indicate that although Catholics were barred from Georgia from its founding by Oglethorpe in 1733 until the expiration of its charter in 1752, when it became a royal colony, they were present in the Augusta area from the time of the earliest explorations. The first visit of Catholics to the Augusta area is recorded as 1540, with DeSoto's expedition. A generation later, Captain John Pardo and his expedition from St. Augustine came to Augusta. In 1755 a group of Acadians, in exile, came to Augusta but were received with such hostility that they settled in the Carolinas instead. Augusta eventually began to be settled by Catholics from France and Ireland. In 1810, a charter of incorporation was obtained from the State Legislature, and the number of Catholics had increased so far as to justify the residence of a pastor.

Under the direction of the first pastor, Rev. Dr. Robert Brown, the congregation raised funds to erect the first Roman Catholic Church in Augusta. Construction began in 1812 and two years later the church was finished. The church and its congregation provided valuable service to the Augusta community. Father Barry, who was well-known by the congregation for his "religious zeal, acts of charity and untiring devotion to the sick and poor of the city", willingly offered the services of the church during the 1839 and 1854 Yellow Fever epidemics that plaguaged Augusta and the surrounding areas. The church rectory was turned into a temporary hospital and the priest's house was turned into an orphanage where the children were cared for whose parents died as a result of Yellow Fever.

By 1843 the congregation had outgrown the church. A resolution to enlarge the building by adding a transept to the existing nave was passed. Finally, ten years later, the parishioners decided that even with the added space, the first Church would not be adequate. Plans to build a "structure worthy of the second city of the state" began.

The collection of building funds proceeded over the next few years interrupted only by the Yellow Fever epidemic of 1854. The cornerstone was laid July 19, 1857 and a system of weekly contribution began.

Construction of the church was done as funds became available. When funds ran low the parishioners donated their time and skills to the building of the church after working a full day at their regular jobs.

The outbreak of the Civil War created further obstacles to the completion of the church. The blockade, set up by the northern army, hindered the passage of valuable building material and artists from the northern states necessary to complete the church. Baltimore artist John Mullen ran the blockade to complete the three marble altars in the church. The Jardine organ, contracted for in the north and too bulky to be smuggled through the blockade, did not arrive until 1868. Resulting economic pressures of the war delayed the construction of the bell tower until 1889-1894. The church was finally consecrated on April 12, 1863. The final cost of the church was $42,833.32.

The new Church, as well as the old one which it replaced, was under the title and name of the Church of the Most Holy Trinity. But as the custom of the church requires a Patron Saint or Saints, the Primary Saint Patron of the church is St Patrick, who was chosen as such by a vote of the clergy and people on Easter Sunday of 1863. The secondary Patron is St. Vincent de Paul, under whose invocation the Church was placed at the laying of the cornerstone. The church was popularly known as St. Patrick's from 1863 until the down town churches merged in 1971.