South Carolina ( KARR-ə-LIE-nə) is a state in the coastal Southeastern region of the United States. It borders North Carolina to the north, the Atlantic Ocean to the southeast, and Georgia to the southwest across the Savannah River. Along with North Carolina, it makes up the Carolinas region of the East Coast. South Carolina is the 40th-largest and 23rd-most populous U.S. state with a recorded population of 5,118,425 according to the 2020 census. In 2019, its GDP was $213.45 billion. South Carolina is composed of 46 counties. The capital is Columbia with a population of 136,632 in 2020; while its most populous city is Charleston with a 2020 population of 150,227. The Greenville-Spartanburg-Anderson, SC Combined Statistical Area is the most populous combined metropolitan area in the state, with an estimated 2023 population of 1,590,636. South Carolina was named in honor of King Charles I of England, who first formed the English colony, with Carolus being Latin for "Charles". In 1712 the Province of South Carolina was formed. One of the original Thirteen Colonies, South Carolina became a royal colony in 1719. During the American Revolutionary War, South Carolina was the site of major activity among the American colonies, with more than 200 battles and skirmishes fought within the state. South Carolina became the eighth state to ratify the U.S. Constitution on May 23, 1788. A slave state, it was the first state to vote in favor of secession from the Union on December 20, 1860. After the American Civil War, it was readmitted to the Union on July 9, 1868. During the early-to-mid 20th century, the state started to see economic progress as many textile mills and factories were built across the state. The civil rights movement of the mid-20th century helped end segregation and legal discrimination policies within the state. Economic diversification in South Carolina continued to pick up speed during and in the ensuing decades after World War II. In the early 21st century, South Carolina's economy is based on industries such as aerospace, agribusiness, automotive manufacturing, and tourism. Within South Carolina from east to west are three main geographic regions, the Atlantic coastal plain, the Piedmont, and the Blue Ridge Mountains in the northwestern corner of Upstate South Carolina. South Carolina has primarily a humid subtropical climate, with hot, humid summers and mild winters. Areas in the Upstate have a subtropical highland climate. Along South Carolina's eastern coastal plain are many salt marshes and estuaries. South Carolina's southeastern Lowcountry contains portions of the Sea Islands, a chain of barrier islands along the Atlantic Ocean.