The Niobrara River, east of Valentine, was recognized by Congress in 1991 as a river that warrants special recognition and protection because of its beauty, biological significance, and paleontological resources. Along the Niobrara River Valley air masses of the humid east and the dry west collide, resulting a rare confluence of many ecosystems, including the northern boreal forest, ponderosa pine forest, eastern deciduous forest, tall grass prairie, and the short grass prairie.