The Roman Catholic Diocese of Baltimore is promoted to an archdiocese, with the founding of the dioceses of New York, Philadelphia, Boston, and Bardstown (now Louisville) by Pope Pius VII.

Pope Pius VII (Italian: Pio VII; born Barnaba Niccol Maria Luigi Chiaramonti; 14 August 1742 20 August 1823), was head of the Catholic Church and ruler of the Papal States from 14 March 1800 to his death in 1823. Chiaramonti was also a monk of the Order of Saint Benedict in addition to being a well-known theologian and bishop.

Chiaramonti was made Bishop of Tivoli in 1782, and resigned that position upon his appointment as Bishop of Imola in 1785. That same year, he was made a cardinal. In 1789, the French Revolution took place, and as a result a series of anti-clerical governments came into power in the country. In 1796, during the French Revolutionary Wars, French troops under Napoleon Bonaparte invaded Rome and captured Pope Pius VI, taking him as a prisoner to France, where he died in 1799. The following year, after a sede vacante period lasting approximately six months, Chiaramonti was elected to the papacy, taking the name Pius VII.

Pius at first attempted to take a cautious approach in dealing with Napoleon. With him he signed the Concordat of 1801, through which he succeeded in guaranteeing religious freedom for Catholics living in France, and was present at his coronation as Emperor of the French in 1804. In 1809, however, during the Napoleonic Wars, Napoleon once again invaded the Papal States, resulting in his excommunication through the papal bull Quum memoranda. Pius VII was taken prisoner and transported to France. He remained there until 1814 when, after the French were defeated, he was permitted to return to Rome, where he was greeted warmly as a hero and defender of the faith.

Pius lived the remainder of his life in relative peace. His papacy saw a significant growth of the Catholic Church in the United States, where Pius established several new dioceses. Pius VII died in 1823 at age 81.

In 2007, Pope Benedict XVI began the process towards canonizing him as a saint, and he was granted the title Servant of God.

The Metropolitan Archdiocese of Baltimore (Latin: Archidiœcesis Baltimorensis) is the premier (or first) see of the Latin Church of the Catholic Church in the United States. The archdiocese comprises the City of Baltimore and 9 of Maryland's 23 counties in the central and western portions of the state: Allegany, Anne Arundel, Baltimore, Carroll, Frederick, Garrett, Harford, Howard, and Washington. The archdiocese is the metropolitan see of the larger regional Ecclesiastical Province of Baltimore. The Archdiocese of Washington was originally part of the Archdiocese of Baltimore.

The Archdiocese of Baltimore is the oldest diocese in the United States whose see city was entirely within the nation's boundaries when the United States declared its independence in 1776. The Holy See granted the archbishop of Baltimore the right of precedence in the nation at liturgies, meetings, and Plenary Councils on August 15, 1859. Although the Archdiocese of Baltimore does not enjoy "primatial" status, it is the premier episcopal see of the Roman Catholic Church in the United States of America, as "prerogative of place".

Within the archdiocese are 518,000 Catholics, 145 parishes, 545 priests (244 diocesan priests, 196 priests resident in diocese), 159 permanent deacons, 55 brothers, 803 sisters, five hospitals, 28 aged homes, 7 diocesan/parish high schools, 13 private high schools, and 4 Catholic colleges/universities.

The Archdiocese of Baltimore has two major seminaries: St. Mary's Seminary and University in Baltimore and Mount St. Mary's Seminary in Emmitsburg.This archdiocese was featured in the Netflix documentary The Keepers exposing the sexual abuse history at Archbishop Keough High School and the murder of Sister Catherine Cesnik in 1969. It was revealed in late 2016 that the Archdiocese of Baltimore had paid off numerous settlements since 2011 for abuse victims.