Centralia is a city in Audrain and Boone counties in the U.S. state of Missouri. The population was 4,027 at the 2010 census, with an estimated population of 4,136 in 2012. The Boone County portion of Centralia (by far the majority of the city) is part of the Columbia Metropolitan Statistical Area, while the Audrain County portion is part of the Mexico Micropolitan Statistical Area.