|Kansas is among the most productive agricultural states of the US, which leads the nation in the production of crops like wheat, sunflower and sorghum. The state is located in the central region of the country, which is commonly known as the "American Heartland". The neighboring states include Nebraska on the north, Oklahoma on the the south, Missouri on the east and Colorado on the west. The state is named after the Kansas river, which in turn got its name from the Kaw tribe, who were the original inhabitants the area. Spread in a total area of 82,277 square miles, Kansas is 15th largest among the states of the USA by size. On the other hand, it is ranked 33rd in terms of population, which was estimated to be 2,802,134 in 2008. Mount Sunflower, a mountain located one half mile from the Colorado border, is the tallest mountain with a height of 4,039 feet. The lowest point, on the other hand, is 679 feet deep and is found in the Verdigris river. Kansas joined the Union in 1861 as a fee state and became the 34th state of the United States. There are 105 counties and 628 cities in Kansas. Wichita is the largest city while Topeka is the capital of the state.