Stock Photo - The Ohio River makes two 90-degree direction changes before the river begins its southwesterly trek to eventually join the Mississippi River near Cario, Illinois. The first change occurs northwest of Pittsburgh, Pennsylvania and the second change takes place north of Steubenville, Ohio. The location of Pittsburgh can only be determined by finding the confluence of the Monongahela River (the winding, north flowing river), and the southwest flowing Allegheny River (lower left quadrant of the image). The large highly reflective spot west of Pittsburgh (near the bottom center) is the location of the Greater Pittsburgh International Airport. The broad expanse of terrain in this image, consisting of meandering rivers and dissected plateaus, is considered to be part of the Allegheny Plateau. The dark linear feature along the southwest edge of the scene (upper left) is Chestnut Ridge, an elevated, forested, upland, which is part of the Allegheny Mountain system.