Mercer County, ND adjoins Oliver near Beulah metropolitan centre yielding a 2020 estimated census population standing at 8,600 making it the 3rd most populous county situated hereabouts. Its county seat is Beulah with other towns include Hazen & Zap-Beulah itself corresponds out to Mercer’s biggesttown aside from recognized country seat. This area had been established out of Oliver and Burleigh Counties back in 1910 when local residents petitioned for new administrative boundaries - posthumously named after Pennsylvania Governor William F Mercer commanding state during period Franklin Pierce .