It is located in the hub of the pioneer "Chouteau's Landing" District, one of the early commercial and residential neighborhoods where the German immigrants settled in pre-Civil War era St. Louis.

It took its name from a noted feast day proclaimed by Pope Pius V to celebrate the victory of the Christian Navy over Islamic forces in the Battle of Lepanto, off the coast of Italy in the Adriatic Sea in 1571.

It also has an indulgenced High Altar (where hundreds of relics of saints are entombed) bestowed by Pope Leo XIII in the late 19th century.

It also provided a temporary home to a small community of Lebanese immigrants in the 20th-century, who went on to found a church in their own—present-day St. Raymond Maronite Cathedral in LaSalle Park neighborhood.

The main altar of the church also has an Indulgence attached to it by Pope Leo XIII in 1896, granting temporal remission of sins at the time of death for those Catholics saying the specific prayers, and dying in the state of grace.

[2] George I. Barnett and Franz Saler, the distinguished architects of St. Mary's Church, designed it in accordance with that of the early 16th-Century Mannerist style.

The altars, statuary, steepled baptismal font, communion rail, carvings and frescoes were all conceived and executed by Schneiderhahn, who also painted the Stations of the Cross.

Within its hallowed walls are also other liturgical art treasures and fixtures donated at later dates by other Roman Catholic religious orders and communities in the metro St. Louis area, particularly those of German origin, including the School Sisters of Notre Dame, the Franciscan Sisters of Mary, the Mill Hill Fathers, and the group promoting the canonization of Blessed Francis X. Seelos, C.SS.R., a Bavarian Redemptorist immigrant priest who worked with mid-19th century German immigrants in St. Louis, Baltimore, and New Orleans.

(His statue, minted by the Vatican Statuary Foundry, stands on a reconstructed side altar made of the communion rail from the old St. Malachy's Church in the Mill Creek Valley (now demolished), once used by the later-dated, now-closed St. Timothy Parish in Affton, MO.

The Hungarian Roman Catholic faith community also honors the famed Joseph Cardinal Mindszenty of Hungary with a carved white marble plaque in the sanctuary, noting his visit to this church in the 1970s.