Complex sentence: MaggieMoo's and Marble Slab Creamery had their headquarters in an unincorporated area in the county, however, now those companies are located in neighboring Gwinnett County in Norcross.
Split into simpler sentences: MaggieMoo's and Marble Slab Creamery had their headquarters in an unincorporated area in the county. Now those companies are located in neighboring Gwinnett County in Norcross.