The history of Pittsburgh started with centuries of Native American civilization in the modern Pittsburgh region. French and British explorers encountered the strategic juncture where the Allegheny and Monongahela rivers meet to form the Ohio river. This area became a battleground, where France and Britain fought for control in the 1750's. Following World War II, Pittsburgh launched a clean air and civic revitalization project known as the "Renaissance". Despite the flourishing service, education, medicine, arts and high tech sectors; Pittsburgh still faces many problems including poverty, crime and pollution.