Complex sentence: NCR had been based in Dayton, Ohio, starting in 1884, but in June 2009 the company sold most of the Dayton properties and moved its headquarters to the Atlanta metropolitan area in unincorporated Gwinnett County, Georgia, near Duluth and Alpharetta.
Split into simpler sentences: NCR had been based in Dayton, Ohio, starting in 1884, but in June 2009 the company sold most of the Dayton properties and moved its headquarters to the Atlanta metropolitan area. Currently the headquarters are in unincorporated Gwinnett County, Georgia, near Duluth and Alpharetta.