I am town historian of Cohocton, Steuben County, NY, which includes the hamlet of Atlanta.  The post office and railroad station at that place were named "Atlanta" in 1892, at the request of the local citizenry.  The place was formerly known as "Blood's Depot," from the last name of an early settler.

The former Cohocton town historian, W. Merle Wheaton, born in 1911 and now deceased, lived his whole life in Atlanta and vicinity.  He knew most of the older residents, but he was never able to learn why the name "Atlanta" was chosen.  I suspect that "Blood's" was considered an unpleasant name, and that Atlanta was chosen because it commemorated a Union victory in the Civil War, and because it sounded better.

Jim Folts
Cohocton Town Historian
PO Box 327
Cohocton, NY 14826