McKim was born in Brandywine in the Delaware Colony.
After pursuing an academic course he moved to Baltimore, Maryland, and served as a member of the Maryland House of Delegates in 1778.
After the war, he served as member of the Maryland Senate from 1806 to 1810.
He also served as justice of court of quarter sessions, and was presiding judge of the Baltimore County Orphans' Court at the time of his death in Baltimore.
This article incorporates public domain material from the Biographical Directory of the United States Congress