The Roman Catholic Archdiocese of Chicago is an ecclesiastical jurisdiction or archdiocese of the Catholic Church located in the northeastern part of the U.S. state of Illinois. It was established as a diocese in 1843 and elevated to an archdiocese in 1880. The archdiocese serves more than 2.2 million Catholics in Cook and Lake counties in the state of Illinois, an area of 1,411 square miles (3,650 km2). The archdiocese is divided into six vicariates and 31 deaneries.