'86". Tennessee celebrated its bicentennial in 1996 with a yearlong celebration called "Tennessee 200". A new state park that traces the state's history, Bicentennial Mall, was opened at the foot of Capitol Hill in Nashville. The same year, the whitewater slalom events at the Atlanta Summer Olympic Games were held on the Ocoee River in Polk County. In 2002, Tennessee amended its constitution to establish a lottery. In 2006, the state constitution was amended to outlaw same-sex marriage. This amendment was invalidated by the 2015 U.S. Supreme Court case Obergefell v. Hodges. On December 23, 2008, the largest industrial waste spill in United States history occurred at TVA's Kingston Fossil Plant when more than 1.1 billion gallons of coal ash slurry was accidentally released into the Emory and Clinch Rivers. The cleanup cost more than $1 billion and lasted until 2015. Geography Tennessee is in the Southeastern United States. Culturally, most of the state is considered part of the Upland South, and the eastern third is part of Appalachia. Tennessee covers roughly , of which , or 2.2%, is water. It is the 16th smallest state in land area. The state is about long from east to west and wide from north to south. Tennessee is geographically, culturally, economically, and legally divided into three Grand Divisions: East Tennessee, Middle Tennessee, and West Tennessee. It borders eight other states: Kentucky and Virginia to the north, North Carolina to the east, Georgia, Alabama, and Mississippi on the south, and Arkansas and Missouri on the west. It is tied with Missouri as the state bordering the most other states. Tennessee is trisected by the Tennessee River, and its geographical center is in Murfreesboro. Nearly three–fourths of the state is in the Central Time Zone, with most of East Tennessee on Eastern Time. The Tennessee River forms most of the division between Middle and West Tennessee. Tennessee's eastern boundary roughly follows the highest crests of the Blue Ridge Mountains, and the Mississippi River forms its western boundary. Due to flooding of the Mississippi that has changed its path, the state's western boundary deviates from the river in some places. The northern border was originally defined as 36°30′ north latitude and the Royal Colonial Boundary of 1665, but due to faulty surveys, begins north of this line in the east, and to the west, gradually veers north before shifting south onto the actual 36°30′ parallel