Charleston is the largest city in the U.S. state of South Carolina. The city is the county seat of Charleston County, and the principal city in the Charleston–North Charleston–Summerville Metropolitan Statistical Area. The city lies just south of the geographical midpoint of South Carolina's coastline and is located on Charleston Harbor, an inlet of the Atlantic Ocean formed by the confluence of the Ashley, Cooper, and Wando rivers. Charleston had an estimated population of 136,208 in 2018. The estimated population of the Charleston metropolitan area, comprising Berkeley, Charleston, and Dorchester counties, was 802,122 residents as of July 1, 2019, the third-largest in the state and the 74th-largest metropolitan statistical area in the United States.