St. Louis Cathedral from across Jackson Square. Cathedral of Saint Louis King of France, A Minor Basilica established as a Parish in 1720 in New Orleans, Louisiana. It was built between 1789 and 1794. The Cabildo stands on its left and the Presbytere on its right; the three buildings face the Mississippi River. Bounding Jackson Square on the right and left just out of the picture are the Pontalba Mansions. The Lousiana Purchase was signed in the Cabildo. Twenty-one years later, in 1994 Ruth and I would return as guests for the wedding of Harry Connick Jr. and Jill Goodacre in St. Louis Cathedral.