Mariano Simon Garriga, third bishop of the Catholic Diocese of Corpus Christi, son of Frank and Elizabeth (Baker) Garriga, was born in Point Isabel (now Port Isabel), Texas, on May 30, 1886. He attended school in Point Isabel, Brownsville, and San Antonio. He also studied at St. Mary's College in Kansas City and St. Francis Seminary in Milwaukee. He was ordained a priest in San Antonio on July 2, 1911. In 1911–12 he served as assistant to the diocesan chancellor in San Antonio. In 1912 he was appointed assistant pastor to the Marfa parish and its missions. In this capacity he traveled across West Texas and into New Mexico on horseback. In 1915 he was recalled to San Antonio to be vice rector of the newly established diocesan seminary, St. John's. He went into service as a national guard chaplain in World War I and trained with the 144th Infantry, Thirty-Sixth Infantry Division. He served in all its engagements in France. During World War II he was appointed vicar delegate for Texas and Louisiana in the military ordinariate of the United States.
Between 1919 and 1936 Garriga was pastor of St. Cecilia's Church in San Antonio. For a brief period after the war he served as president of Incarnate Word College. From 1921 to 1936 he also taught at St. John's. In 1926 he was appointed historian of the Catholic Archdiocese of San Antonio. The restoration work of San José y San Miguel de Aguayo Mission was carried out under his supervision. In 1935 he was invested as a domestic prelate, and on September 21, 1936, he was consecrated titular bishop of Siene and coadjutor of Corpus Christi, with right of succession. He was the first bishop of a Texas diocese to be born in the state. From 1936 to 1948 he also served as pastor of St. Peter's in Laredo. On March 15, 1949, Bishop Emmanuel B. Ledvina of the Corpus Christi diocese retired, and Bishop Garriga took over his administration.
Garriga was a member of the Knights of Columbus, Veterans of Foreign Wars, Texas Historical Commission, Order of the Alhambra, and Order of the Holy Sepulchre of Jerusalem. In 1936 he received an honorary doctorate of laws from St. Edward's University in Austin. He died on February 21, 1965, in Corpus Christi, and was interred in the crypt of Corpus Christi Cathedral.