Question: The largest county in Oklahoma by area, gets its name from the broad rolling hills and rolling tallgrass prairie and Cross Timbers encompassing the county and surrounding areas, including portions of Mayes, Tulsa, Washington and Kay Counties, was created in what year?

 The name refers to the broad rolling hills and rolling tallgrass prairie and Cross Timbers encompassing Osage County and surrounding areas, including portions of Mayes, Tulsa, Washington and Kay Counties.  The Osage is the southern extension of the Flint Hills of Kansas. The Osage Hills is a hilly area in Oklahoma, commonly known as "The Osage". <SEP>  Created in 1907 when Oklahoma was admitted as a state, the county is named for and is home to the federally recognized Osage Nation.  The county is coextensive with the Osage Nation Reservation, established by treaty in the 19th century when the Osage relocated there from Kansas.  The county seat is in Pawhuska, Oklahoma, one of the first three towns established in the county. Osage County is the largest county by area in the state of Oklahoma in the United States.  The total population of the county is 47,987. <SEP> The Tallgrass Prairie Preserve, located in Osage County, Oklahoma near Foraker, Oklahoma, is owned and managed by The Nature Conservancy.  It is protected as the largest tract of remaining tallgrass prairie in the world.  The preserve contains 39000 acre owned by the Conservancy and another 6000 acre leased in what was the original tallgrass region of the Great Plains that stretched from Texas to Manitoba. <SEP> The Osage Plains are a physiographic section of the larger Central Lowland province, which in turn is part of the larger Interior Plains physiographic division.  The area is sometimes called the Lower Plains, North Central Plains, and the Rolling Plains.  The Osage Plains, covering west-central Missouri, the southeastern third of Kansas, most of central Oklahoma, and extending into north-central Texas, is the southernmost of three tallgrass prairie physiographic areas.  It grades into savanna and woodland to the east and south, and into shorter mixed-grass prairie to the west.  The Osage Plains consist of three subregions.  The Osage Plains proper occupy the northeast segment.  Although sharply demarcated from the Ozark uplift, the Plains are nonetheless a transitional area across which the boundary between prairie and woodland has shifted over time.  In the central portion of the physiographic area lies the second subregion, the Flint Hills, commonly called "The Osage" in Oklahoma.  This large remnant core of native tallgrass prairie is a rocky rolling terrain that run from north to south across Kansas and extends into Oklahoma.  To the west and south of these hills are the Blackland Prairies and Cross Timbers.  This vegetatively complex region of intermixed prairie and scrubby juniper-mesquite woodland extends into north-central Texas.  Bluestem prairies and oak-dominated savannas and woodlands characterize the natural vegetation in the Cross Timbers.  Much of the area has been converted to agriculture, although expanses of oak forest and woodland are still scattered throughout the eastern portion of the subregion.