8th largest Diocese in the nation serving approx. 1.4 million Catholics through 134 parishes, 56 Catholic Schools & the Seminary of the Immaculate Conception The Catholic Church on Long Island The Diocese of Rockville Centre on Long Island was 1957 and covers 1,109 square miles in Nassau and Suffolk counties. It is the 8th largest diocese in the United States. The diocese serves approximately 1,428,296 baptized Catholics and is comprised of 133 parishes (plus one campus parish) in 115 towns. Under the direction of our Bishop, John O. Barres our mission is Dramatic Missionary Growth: to evangelize, strengthen and propagate the Roman Catholic faith. We are committed to providing vibrant parishes in which to worship and receive the Sacraments; outstanding Catholic education; a healthcare system grounded in Catholic moral teaching, pastoral care; a premier social service agency, Catholic Charities; faith-based ministries; and a multimedia network, the Catholic Faith Network.