Simplify the following text for a Grade 15 native English-speaking person.
Original: Northwestern Oklahoma is the geographical region of the state of Oklahoma which includes the Oklahoma Panhandle and a majority of the Cherokee Outlet , stretching to an eastern extent along Interstate 35 , and its southern extent along the Canadian River to Noble County .
Simplified: Northwestern Oklahoma is the geographical region of the state of Oklahoma which includes the Oklahoma Panhandle , stretching to an eastern extent along Interstate 35 , and its southern extent along the Canadian River to Noble County .