The Roman Catholic Archdiocese of Chicago (Latin: Archidioecesis Chicagiensis) was established as a diocese in 1843 and elevated to an archdiocese in 1880. It serves the more than 2.3 million Catholics in Cook and Lake counties in Northeastern Illinois, a geographic area of 1,411 square miles (3,650 km2). The archdiocese is divided into six vicariates and 31 deaneries. This local church is headed by His Eminence Blase Joseph Cupich, Cardinal, Archbishop of Chicago, assisted by six episcopal vicars, each responsible for a vicariate (region). The see city for the diocese is Chicago. The cathedral parish for the archdiocese is the Holy Name. A French Jesuit missionary, the Rev. Jacques Marquette, SJ first explored the area that is now Chicago in the mid-17th century. On December 4, 1674, Father Marquette arrived at the mouth of the Chicago River where he built a cabin to recuperate from his travels. His cabin became the first European settlement in the area now known as Chicago. Marquette published his survey of the new territories and soon more French missionaries and settlers arrived. In 1795, the Potawatomi tribe signed the Treaty of Greenville that ceded to the United States a tract of land at the mouth of the Chicago River. There in 1804, Fort Dearborn was erected and protected newly arrived Catholic pioneers. In 1822, Alexander Beaubien became the first person to be baptized in Chicago. In 1833, Jesuit missionaries wrote a letter to the Most Rev. Joseph Rosati, Bishop of Saint Louis and Vicar General of Bardstown, pleading for the appointment of a resident pastor to serve over one hundred professing Roman Catholics living in Chicago. Rosati appointed a diocesan priest, the Rev. John Mary Irenaeus Saint Cyr. Fr. Saint Cyr celebrated his first Mass in a log cabin owned by the Beaubien family on Lake Street, near Market Street, in 1833.