O'Neill, Pennington Co., SD - 1909 Business Directory This file contains a listing from the "South Dakota State Business Directory", published in 1909 by the Gazetteer Publishing Co., Denver, CO. This information was transcribed by Deb Hochhalter and may be used for personal, non-profit use only. All other rights reserved. Deb Hochhalter 1997 O'Neill A new postoffice in Pennington County, 20 miles from the nearest railroad point. Population 6. Last Name First Name Business O'Neill Lafayette Postmaster, farmer and stock grower.