Virginia (/vərˈdʒɪniə/ (listen)), officially the Commonwealth of Virginia, is a state in the Southeastern and Mid-Atlantic regions of the United States located between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are shaped by the Blue Ridge Mountains and the Chesapeake Bay, which provide habitat for much of its flora and fauna. The capital of the Commonwealth is Richmond; Virginia Beach is the most populous city, and Fairfax County is the most populous political subdivision. The Commonwealth's estimated population as of 2018[update] is over 8.5 million. The area's history begins with several indigenous groups, including the Powhatan. In 1607 the London Company established the Colony of Virginia as the first permanent English colony in the New World. Virginia's state nickname, the Old Dominion, is a reference to this status. Slave labor and the land acquired from displaced Native American tribes each played a significant role in the colony's early politics and plantation economy. Virginia was one of the 13 Colonies in the American Revolution. In the American Civil War, Virginia's Secession Convention resolved to join the Confederacy, and Virginia's First Wheeling Convention resolved to remain in the Union; that led to the creation of West Virginia. Although the Commonwealth was under one-party rule for nearly a century following Reconstruction, both major national parties are competitive in modern Virginia. The Virginia General Assembly is the oldest continuous law-making body in the New World. The state government was ranked most effective by the Pew Center on the States in both 2005 and 2008. It is unique in how it treats cities and counties equally, manages local roads, and prohibits its governors from serving consecutive terms. Virginia's economy has many sectors: agriculture in the Shenandoah Valley; federal agencies in Northern Virginia, including the headquarters of the U.S. Department of Defense and Central Intelligence Agency (CIA); and military facilities in Hampton Roads, the site of the region's main seaport.