Columbus is a consolidated city-county located on the west-central border of the U.S. state of Georgia. Located on the Chattahoochee River directly across from Phenix City, Alabama, Columbus is the county seat of Muscogee County, with which it officially merged in 1970. Columbus is the third-largest city in Georgia and the fourth-largest metropolitan area. According to the 2018 estimates from the U.S. Census Bureau, Columbus has a population of 194,160 residents, with 303,811 in the Columbus metropolitan area. The metro area joins the nearby Alabama cities of Auburn and Opelika to form the Columbus–Auburn–Opelika Combined Statistical Area, which has a 2017 estimated population of 499,128.