Green Country, sometimes referred to as Northeast Oklahoma, is the northeastern portion of the U.S. state of Oklahoma, which lies west of the northern half of Arkansas, the southwestern corner the way of Missouri, and south of Kansas. Alternate definitions While the name's usage can be traced to the early part of the 20th century, it was popularized in the 1960s by the Oklahoma Department of Tourism and Recreation as one of six travel destination regions within the state. Said tourism designation is an 18-county region including Pawnee, Osage, Washington, Nowata, Craig, Ottawa, Delaware, Mayes, Rogers, Creek, Tulsa, Wagoner, Cherokee, Adair, Sequoyah, Muskogee, Okmulgee, and McIntosh counties. Another alternate usage of the term can include solely the immediate vicinity of Green Country's principal city, Tulsa; the Tulsa Metropolitan Area or the city of Tulsa proper is often referred to as "Green Country" in its own right. In this case, the terms "Tulsa Metropolitan Area" and "Green Country" are used interchangeably. Average precipitation totals in Green Country are generally above 40 inches per year. The area is also one of the most populous regions of Oklahoma, and is home to some of its largest cities. Geography Northeastern Oklahoma has the state's second largest city, Tulsa. In addition to the area's foliage and rolling hills, it has more lakes than any other geographical area of Oklahoma, as well as more than half of the state's registered state parks. Oklahoma is one of only four states with more than 10 ecoregions, but six of its 11 ecoregions are located in northeastern Oklahoma. The heavily wooded Ozark Mountains and their foothills dominate most of northeast Oklahoma from the immediate Tulsa vicinity south and eastward towards the Arkansas state line, containing both evergreen pine and deciduous forests. In its western counties, the far eastern extent of the Great Plains transition to woodlands through the Cross Timbers region. This area includes most of Oklahoma's portion of the Flint Hills, some of which is the protected by the Tallgrass Prairie Preserve near Pawhuska, one of the last remnants of tallgrass prairie in the United States. Prairie terrain is most apparent in a strip of Green Country's northern section, which borders Kansas, running roughly from Bartlesville to Miami, where the landscape is a mix of true prairie and forest. A small portion of the Ouachita Mountains extend into the southern areas of northeast Oklahoma, though the Ozark highlands