Complex sentence: His father may have been Christopher Sheldes, a white wagon driver, who worked at Mount Vernon until December 1773 and he is listed as "11 yrs. old" in the February 1786 Mount Vernon Slave Census.
Split into simpler sentences: His father may have been Christopher Sheldes, a white wagon driver, who worked at Mount Vernon until December 1773. Shields is listed as "11 yrs. old" in the February 1786 Mount Vernon Slave Census.