The Diocese of Baltimore was established in 1789 as the first Catholic diocese in the United States, with John Carroll as its first bishop, and was elevated to an archdiocese in 1808 when Carroll became its first archbishop. It is regarded as the premier see of the Roman Catholic Church in the United States. Its co-cathedral, the Basilica of the National Shrine of the Assumption of the Blessed Virgin Mary, was the first cathedral built in the country, completed in 1821.