Re: Mary Avis?
If we're thinking of the same Mary Avis, she's buried in St. Augustine's cemetery in Perry County, Indiana. She followed her son (James) and daughter (Sally Avis Wheatley) there. Her tombstone indicates that she was born around 1770 and was the wife of John.
John first shows up in St. Mary's County, Maryland around 1794 when he is part of the Maryland Militia. He then shows up on the 1800 census and, in 1803, performs accounting work for his wife's sister, Eleanor Thomas, when some of her husband's children die. He's still there in 1810, but then disappears.
It is believed that Mary's maiden name was Manly and her father was a Basil Manly. I'm not sure if he's the Captain Basil Manly who served in the Revolutionary War. Mary, Eleanor and Ann are mentioned in the will of their mother, Ann Teare Manly.