DeKalb County is a county located in the U.S. state of Missouri. As of 2010, the population is 12,892. The county was organized in 1845 and is named after the American Revolutionary War general Johann de Kalb. The county along with Buchanan and Andrew counties in Missouri and Doniphan County, Kansas, is included in the St. Joseph Metropolitan Statistical Area, which had an estimated population of 122,306 in 2006. The county seat of DeKalb County is Maysville, while the largest city in the county is Cameron.

According to the 2000 census, the county has a total area of 425.77 square miles (1,102.7 km²), of which 424.20 square miles (1,098.7 km²) (or 99.63%) is land and 1.57 square miles (4.1 km²) (or 0.37%) is water.

As of the census of 2000, there were 11,597 people, 3,528 households, and 2,473 families residing in the county. The population density was 27 people per square mile (11/km²). There were 3,839 housing units at an average density of 9 per square mile (3/km²). The racial makeup of the county was 89.09% White, 8.86% Black or African American, 0.66% Native American, 0.17% Asian, 0.01% Pacific Rim Islander, 0.27% from other races, and 0.93% from two or more races. 1.08% of the population were Hispanic or Latino of any race.

Missouri (ⁱ/mɨˈzʊəri/) (nickname The Show Me State) is a U.S. state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. Missouri is the 21st most extensive and the 18th most populous of the 50 United States. Missouri comprises 114 counties and the independent city of St. Louis. The four largest urban areas are St. Louis, Kansas City, Springfield, and Columbia. Missouri's capital is Jefferson City. The land that is now Missouri was acquired from France as part of the Louisiana Purchase and became known as the Missouri Territory. Part of the Territory was admitted into the union as the 24th state on August 10, 1821.

Missouri generally mirrors the demographic, economic and political makeup of America and has long been considered a political bellwether state. With the exceptions of the Presidential elections of 1956 and 2008, Missouri's results have accurately predicted the next President of the United States in every election since 1904. It has both Midwestern and Southern cultural influences, reflecting its history as a border state. It is also a transition between the Eastern and Western United States, as St. Louis is often called the "western-most Eastern city" and Kansas City the "eastern-most Western city". Missouri's geography is highly varied. The northern part of the state lies in dissected till plains while the southern part lies in the Ozark Mountains (a dissected plateau), with the Missouri River dividing the two. The state lies at the intersection of the three greatest rivers of North America, with the confluence of the Mississippi and Missouri Rivers near St. Louis, and the confluence of the Ohio River with the Mississippi north of the Bootheel. The starting points of the Pony Express Trail and Oregon Trail were both in Missouri. The mean center of United States population as of the 2010 Census is at the town of Plato in Texas County, Missouri.

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