One of one of St. Louis' best-known landmarks is the Basilica of St. Louis, King of France, commonly known as the Old Cathedral. The cathedral is located near the St. Louis Riverfront and is the oldest cathedral west of the Mississippi River. When Pierre Laclede and Auguste Chouteau founded St. Louis in 1764, Laclede set aside a tract of land on the Mississippi River bank for construction of a church and cemetery just west of where he built his home. In 1770 the first Catholic Church in St. Louis, a small log house with St. Louis IX, King of France as its patron saint, was built on this site. In 1776 the mission of St. Louis became a canonical parish and a second log cabin church was built. Its bell, the gift of Spanish Lt. Governor Don Piernos, was enriched by 200 Spanish silver dollars in its casting and can be seen today in the Old Cathedral Museum.

Work commenced on the current building in 1831 and was completed in 1834. The cathedral is made of native limestone with a sandstone facade. The neo-classical interior of the church (photo left) is quite bright due to clear-glass windows and a white color scheme. The sanctuary has a fairly traditional arrangement, with altar rail and central Tabernacle. A large copy of Velazquez' famed "The Crucifixion" painting hangs above the main altar. A portrait of St. Louis IX kneeling in front of an altar on the night before his coronation hangs at the rear of the Cathedral. The portrait was a gift of the Louis XVIII in 1818. Statues of Saint Louis IX and Saint Joan of Arc are near the altar at the front of the Cathedral.
 

From 1826 to 1843, the St. Louis diocese, headquartered at the Old Cathedral, covered nearly half of America, from Louisiana north to Michigan and from Kentucky west to Oregon. The St. Vincent de Paul Society in America was founded in 1845 at this Cathedral. A bronze plaque on the facade of this historic Church commemorates this event. This building was the Cathedral of the Archdiocese of St. Louis until 1914 when the New Cathedral on Lindell Blvd. The official title of Cathedral passed of St. Louis from this from the old building to the new and the original cathedral was then renamed the Church of St. Louis IX, King of France. In 1961, Pope John XXIII signed a decree naming the former Cathedral of St. Louis, a Basilica, recognizing it as "a treasure of the universal church".

In the 1960s when the riverfront area was cleared for construction of the Jefferson National Expansion Memorial, the Old Cathedral was the only building spared. An intensive restoration program was undertaken during that time to restore the original appearance of the Old Cathedral as much as possible. It has been said that the site of the Old Cathedral is the only parcel of land in St. Louis that has been used for the same purpose since the city's founding.