On December 4, 1849, four fathers of the Oblate of Mary Immaculate arrived in Brownsville on horseback to establish a local parish. Seven years later, the Church of the Immaculate Conception was completed, using 250,000 bricks made as tithes by parishioners. Designed by Father Pierre Y. Kerralum, who studied architecture in France before entering the seminary, the church is an excellent example of the Gothic Revival style. Serving as the first Oblate seminary in Texas, it housed priests fleeing revolution in Mexico. The site became a cathedral in 1874 when the Vicariate Apostolic of Brownsville was established.

On the grounds are two memorials: one dedicated to the Oblate missionaries, and a vault belonging to the family of Simon Celaya, a Spanish immigrant and organizer of the Rio Grande Railroad. Stained glass lancet windows lining the nave and apse illuminate the sanctuary. Much of the interior has been restored, including the unique blue canvas lining the vaulted ceiling. The Catherdral is listed on the National Register of Historic Places.