Cornerstone Bank 125 Clairemont Ave, Decatur, GA30030 Cornerstone is a relatively new banking and finance company. Founded in Atlanta in 2001, Cornerstone has only three…More locations. This one, in the heart of downtown Decatur, is the newest facility. It is located in the five-story Two Decatur Town Center Building, where virtually all the other offices are occupied by lawyers and finance businesses. Though limited in the number of physical locations where customers can do their banking, Cornerstone offers almost all of itsservices through its online banking platform.