Leonard Calvert, Governor of the Maryland Colony, appointed her as the executrix of his estate in 1647, at a time of political turmoil and risk to the future of the settlement.

[2] However, in the rough, male-dominated world of the colonies, her stance for her rights and her independence was unusual in actual practice[1] and it would have been fairly uncommon back in England in that period.

Later, Giles Brent transferred a 1,000-acre (4 km2) land tract on Kent Island, Maryland to Margaret as payment of a debt he owed his sister, although he may have continued to manage it himself.

Together they became guardians of seven-year-old Mary Kittamaquund, the daughter of a Piscataway chief, whose deathly ill son had recovered under the ministrations of Jesuit Rev.

Ingle was an ally of Virginia trader William Claiborne who disputed Catholic Giles Brent's establishment of a rival trading post on Kent Island.

Ingall took Acting Governor Giles Brent (who had briefly imprisoned him for high treason the previous year), and both Jesuit priests as prisoners back to England.

[1][7] Governor Leonard Calvert, when he returned, recruited armed men from across the Potomac River in the nearby colony of Virginia for help against the raiders.

[1] Lord Baltimore had always managed his proprietorship from England, where he worked to keep political support for the colony, as well as to prove his loyalty (as a Catholic) to the new government of Protestants.

"[10] Governor Thomas Greene refused her request, as the assembly at the time considered such privileges for women to be reserved for queens.

Some accounts suggest that she had spent all of Leonard Calvert's personal estate by this time, and proceeded to sell Lord Baltimore's cattle to pay the soldiers' wages, although there is disagreement among historians on this matter.

Brent appeared at the assembly a final time as Lord Baltimore's attorney, on February 9, 1648 in a case against Thomas Cornwallis.

[1][6] He may have been suspicious of Brent's motives in managing his assets, or not realized that the colony had been in danger of extinction, had the mercenaries not been paid to leave.

While the assembly had refused to give Margaret Brent a vote, it defended her stewardship of Lord Baltimore's estate,[1] writing to him on April 21, 1649, that it "was better for the Colony's safety at that time in her hands than in any man's ... for the soldiers would never have treated any others with that civility and respect ...".

[6][11] Given Lord Baltimore's (and Governor Stone's) hostility to the Brent family, Giles and his young wife Mary moved to Chopawamsic Island in the Potomac River in 1649, then to Virginia's Northern Neck in 1650.

Historian Lois Greene Carr believes the two sisters had taken vows of celibacy under Mary Ward's Institute in England.