A. Emery, Superior-General of the Sulpicians, deemed it prudent to found a house of their institute in some foreign country, and at the suggestion of Cardinal Antonio Dugnani, nuncio at Paris, the United States was chosen.

They purchased the One Mile Tavern on the edge of the city, dedicated the house to the Blessed Virgin, and in October opened classes with five students whom they had brought from France.

[2] With the help of Bishop John Carroll and others, the Sulpicians were able to purchase additional property adjoining the One Mile Tavern and build St. Mary's College and Seminary on North Paca Street at the developed northwest edge of the newly incorporated city.

It was operated until 1852 by the Sulpicians religious order and graduated hundreds of young men and formed an important educational role in the growing city during the first half of the 19th century.

St. Mary's was established as a theological seminary in 1822 by Pope Pius VII, when it was authorized as the first ecclesiastical faculty in the United States with the right to grant degrees in the name of the Holy See.

The under-graduate secular St. Mary's College closed in 1852 and Archbishop Kenrick asked the Jesuits to oversee the formation of a school.

The lawn was used as a helicopter pad for leaving to the local airport following the several days of the 1995 Baltimore visit by Pope John Paul II.

[3][4] In 1968, reflecting a more ecumenical and outgoing spirit from the Second Vatican Council and with educational partnerships with neighboring Christian traditions/denominations of (Protestant and Eastern Orthodox) in the City and central Maryland region, plus having additional space and resources due to a decline in the number of priests in formation by the late 1960s, an "Ecumenical Institute of Theology" was established in 1968 with a separate board of trustees of lay and clergy members from the Catholic and other partnering faiths and a separate dean/director and began offering courses, programs, events with library resources and religious training on a graduate-level to the laity and clergy of the area, which has since greatly raised the academic levels and religious discourse in the following four decades.

Elizabeth Ann Seton, founder of the Sisters of Charity, pronounced vows of chastity and obedience to John Carroll for one year in the lower chapel on Paca Street on March 25, 1809.

[3] It is the only part of the first group of original seminary/college buildings in Georgian/Federal red brick style from the 1810s which were later razed and a second set of Seminary buildings in a Victorian/French Second Empire style of architecture were erected on the same site facing east on North Paca Street in 1878 and surrounded the original Chapel that is remaining on Paca facing west, into the 21st century.

[8] St. Mary's Ecumenical Institute, founded in 1968, offers graduate degrees and certificates; it supports a diverse adult learning environment of different ethnicities and denominations.