The area in United States west of the Appalachian Mountains and extending vaguely to the Mississippi River, spanning the lower Great Lakes to the upper south, is a region known as trans-Appalachia, particularly when referring to frontier times. It included much of Ohio Country and at least the northern and eastern parts of the Old Southwest. It was never an organized territory or other political unit. Most of what was referred to by this name became the states of western Pennsylvania, Ohio, West Virginia, Kentucky, Tennessee and western Virginia. It is still a vague and little used place name today.