Mary A Marshall was the daughter of James and Margaret Loan.
If you look at the 1850 census, the James Loan family appears in Moyamensing, Philadelphia Co, PA.There is some discrepancy in ages of James and some of the children, but it is clear that it is the same family, with the same children.Mary A. Loan is listed as age 19 (b=1831) in the 1850 census, whereas in 1860, she is listed as 25 (1835).
Mary A Marshall and James L Marshall are in the 1870 census, living with his parents, James and Mary Marshall, with the three children, William, Louis, and Mary E.
I don't have any info on the family of James Loan.There is a record of a James Loan who is naturalized in PA on Oct 6, 1832.No other info is given about him.
Do you have any other info on the Loan children (James, Margaret, and Mary) - spouses, etc?