Judith, there are two men named George Richard KNOWLES around that time.
The first is was born February 12, 1786 to James KNOWLES and Hannah CAMPBELL.
The second is the son of that George Richard KNOWLES and a mulatto slave named Charlotte from his father's plantation. That George Richard was born in 1814 on Long Island, married Mary Eliza TURNQUEST in 1839, and died in 1858.
There is also George Maxwell KNOWLES, son of George Richard Jr. and Mary Eliza. That might the Maxwell you're thinking of. George Maxwell was born February 15, 1861 and married Jessima McNEIL.
I descend from all of the above, so feel free to contact me if you're still around.