One of the wealthiest men in the Americas at that time and a newly elected delegate to the Second Continental Congress and the only Catholic to vote on independence and sign the document, Carroll staked his fortune on the American Revolution.

One of his most important tasks he said was when he helped lay the "first stone" for the new technology of transportation, the Baltimore and Ohio Railroad on Independence Day, July 4, 1828, west of the city near modern Halethorpe.

In 1784, Charles bought Marys Lott, a 75-acre (30 ha) farm from Jacob Burgoon, a Catholic immigrant from Alsace-Lorraine, France, who came to America in about 1745 and settled in Elkridge, Maryland.

Ambrose Maréchal (1764–1828), the future third Archbishop of Baltimore, and other Sulpician priests were frequent guests at Doughoregan, saying Mass there often and gaining the ear of the Charles Carroll.

In 1830, Emily Caton MacTavish, favorite granddaughter of the Signer and sister of the "Three American Graces", convinced Carroll to give 253 acres (1.02 km2) to the Sulpician Fathers for the erection of a minor seminary — Saint Charles.

The park-like grounds of St. Charles looked southeast towards the Frederick Road, later the eastern end of the historic National Road, the first federally sponsored interstate route begun in the early 1800s from Baltimore to Cumberland and on to the western states finally ending near the Mississippi River in Vandalia, Illinois, then the territorial capital of the Territory of Illinois.

In later years the college would overlook Wilkens Avenue, which also runs southwestward out of the city near the intersection of Maiden Choice Lane.

The ruins of the old minor seminary's recreation hall and laundry are now located in the middle of Terra Maria Way circle with the grotto removed for a storm water retention pond.

(39°17′16″N 76°53′15″W / 39.287713°N 76.887635°W / 39.287713; -76.887635)[10][11] In 1969, St. Charles' High School Department with boarding school was closed and the junior college merged with the upper college of St. Mary's Seminary and University now on Roland Avenue and Belvedere Avenue/Northern Parkway in the Roland Park neighborhood of north Baltimore (having moved there from North Paca Street by St. Mary's Street in the old Seton Hill neighborhood to new landmark buildings of Beaux Arts/Classical Revival style architecture on a new expansive park-like campus in 1929).

[12] The chapel, designed by Murphy & Olmsted of Washington, D.C., was known as “Our Lady of the Angels” and was the gift of the Jenkins family, who also built Corpus Christi Church in Baltimore.