Hallowell appears to have had an interest in the firm of McTavish, Frobisher, and Co.

Susan Morris Hallowell was born on June 17, 1845, in Philadelphia, Pennsylvania, daughter of a merchant and banker Morris Longstreth Hallowell (1809-1880).

She was heavily involved in charity work, serving as one of the Philadelphia Society for Organized Charity's "women visitors" (social workers) in the 7th Ward. She was a member of the Board of Managers of the Children's Aid Society and also the Bureau of Information of the State of Pennsylvania. She was never married. She helped to care for her mother and sister Anna (1831–1905) who was active in philanthropic and educational work and was the first woman member of the Philadelphia Board of Public Education (1887-1896). Susan preserved a collection of Hallowell family papers.

She died in June 1940, in Philadelphia County, Pennsylvania.

William Hallowell was born in 1771 and died in 1838. He had purchased a partnership in the North West Company from Alexander Henry in 1798. In the same year, he married Martha Henry (1777-1849) in Albany, New York, who was the daughter of Alexander Henry (the Elder) and an unknown Indigenous woman.