In the above letter he is referring to the town of Satartia, Mississippi, which is in Yazoo County, Mississippi, about 17 miles south of Yazoo City, Mississippi.
I think Mr. A. G. Gale in the above letter is Mr. Abner Greene Gale, whose family owned land near Satartia. His parents were Thomas and Ann Greene Gale.
The following link provides some information about the Gale family: