Mississippi ( (listen)) is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Mississippi's western boundary is largely defined by the Mississippi River. Mississippi is the 32nd largest and 34th-most populous of the 50 U.S. states. Jackson is both the state's capital and largest city. Greater Jackson is the state's most populous metropolitan area, with an estimated population of 580,166 in 2018. On December 10, 1817, Mississippi became the 20th state admitted to the Union. By 1860, Mississippi was the nation's top cotton-producing state and slaves accounted for 55% of the state population. Mississippi declared its secession from the Union on January 9, 1861, and was one of the seven original Confederate States, which constituted the largest slaveholding states in the nation. Following the Civil War, it was restored to the Union on February 23, 1870.Until the Great Migration of the 1930s, African Americans were a majority of Mississippi's population. In 2010, 37.3% of Mississippi's population was African American, the highest percentage of any state. Mississippi was the site of many prominent events during the civil rights movement, including the Ole Miss riot of 1962 by white students objecting to desegregation, the 1963 assassination of Medgar Evers, and the 1964 Freedom Summer murders of three activists working on voting rights. Mississippi is almost entirely within the Gulf coastal plain, and generally consists of lowland plains and low hills. The northwest remainder of the state consists of the Mississippi Delta, a section of the Mississippi Alluvial Plain. Mississippi's highest point is Woodall Mountain at 807 feet (246 m) above sea level adjacent to the Cumberland Plateau; the lowest is the Gulf of Mexico. Mississippi has a humid subtropical climate classification. Mississippi frequently ranks low among U.S. states in measures of health, education, and development, while ranking high in measures of poverty. The adage "Thank God for Mississippi" became popular due to these rankings and is often said by natives of other low-ranking U.S. states, as Mississippi's extremely low ranking usually spares those states from the shame of coming in last place.