Marmaduke was Doorkeeper to the Upper House of Assembly, 1662. [Maryland Heraldic Families.]
In November 1685 Marmaduke Simms, of St. Mary's County had a land patent for 400 A. in Cecil County.
He settled first in St. George's Hundred on the west side of St. George's [now St. Mary's] River. Then he moved to the settlements north of the Wicomico River then in St. Mary's County, but which by a readjustment of the boundaries fell into present Charles County. His seat was known as "St. George's" which he purchased from his neighbor Thomas Simpson. On February 23 1675, as Marmaduke Semme, of St. Mary's County, Innholder, he bought the tract "Middle Plantation" of 300 acres lying on the Sassafras River in Cecil County. On November 14, 1685 , he was granted by Lord Baltimore 400 acres of land lying on the Lek River in Cecil County which he named "Symmes Forrest."