In Mary's death record her mother's maiden name is provided as Margaret Ymer, born in New York. The last name Ymer seems very strange for New York in 1800, so I considered it probable that this is the name Wymer, Wimer, or Weimer. However, although unable to find it in the 1800 census in New York, I was able to find it in the 1810 census for Berlin, Rensselaer, New York, the very town that Charles A. Stuart was born in.