Census: Mecklenburg County’s population hits 1 million. Mecklenburg County topped the one million population mark in 2014, the first county in the Carolinas to do so. New census data being released at 12:01 a.m. Thursday March 26, 2015 shows total Mecklenburg population is 1.01 million, a two percent increase from 2013. Jeff Siner jsiner@charlotteobserver.com. Mecklenburg County topped the one million population mark in 2014, the first county in the Carolinas to do so. New census data being released at 12:01 a.m. Thursday March 26, 2015 shows total Mecklenburg population is 1.01 million, a two percent increase from 2013.