I have visited Stratford Hall, Lee's ancestral home, many times.
You will find a chair in one of the displays, donated by the son of a former slave, Richard M Lee of New York City.
It was written in 1943 and sent to Mrs. Charles Lanier-head of the Robert E. Lee Foundation which was founded to restore Stratford Hall. The letter describes how it came into his possession and how he wanted to donate "because of the kindness shown by Lee to his colored people and how the Lee family carried out the Generals wishes and took care of his people until they died."