The geography of the U.S. State of Colorado is diverse, encompassing both rugged mountainous terrain, vast plains, desert lands, desert canyons, and mesas. Colorado is a landlocked U.S. state. In 1861, the United States Congress defined the boundaries of the new Territory of Colorado exclusively by lines of latitude and longitude, stretching from 37°N to 41°N latitude, and from 102°02'48"W to 109°02'48"W longitude (25°W to 32°W from the Washington Meridian). Starting in 1868, official surveys demarcated the boundaries, deviating from the parallels and meridians in several places. Later surveys attempted to correct some of these mistakes but in 1925 the U.S. Supreme Court affirmed that the earlier demarcation was the official boundary. The borders of Colorado are now officially defined by 697 boundary markers connected by straight boundary lines. Colorado, Wyoming, and Utah are the only states that have their borders defined solely by straight boundary lines with no natural features. The southwest corner of Colorado is the Four Corners Monument at 36°59'56"N, 109°2'43"W. This is the only place in the United States where four states meet: Colorado, New Mexico, Arizona, and Utah. The summit of Mount Elbert at elevation in Lake County is the state's highest point and the highest point in the Rocky Mountains of North America. Colorado has approximately 550 mountain peaks that exceed elevation. Colorado is the only U.S. state that lies entirely above elevation. The state's lowest elevation is at the point on the eastern boundary of Yuma County where the Arikaree River flows into the state of Kansas. As is common in mountainous and adjacent areas, microclimates exist and weather is strongly influenced by orography. A notable regional atmospheric phenomenon is the Denver Convergence Vorticity Zone (DCVZ) and related Denver Cyclone occurring on the High Plains just east of Denver. The Rocky Mountains as a whole induce significant changes in weather afar, such as the Colorado low. Regions To the east of the Rocky Mountains in Colorado are the Colorado Eastern Plains/High Plains, the section of the Great Plains within Colorado at elevations ranging from . The Midwest states of Kansas and Nebraska border Colorado to the east and northeast. The plains are sparsely settled with most population along the South Platte and the Arkansas rivers. Rainfall is meager, averaging about annually. There is some irrigated farming, but much of the land is used for dryland farming or ranching. Winter wheat is a typical