The State of Iowa ( ) is a state in the Midwestern region of the United States of America. It is the 29th state of the United States, having joined the Union on December 28, 1846. The state is named for the Ioway people, a Siouan tribe of Native Americans that formerly lived there. It is officially known as the "Hawkeye State" and unofficially known as the "Tall Corn State".

Geography

The Mississippi River separates Iowa from Illinois and Wisconsin to form the eastern boundary of the state. The Missouri River on the west edge of the state forms the boundary for Nebraska (with the exception of Carter Lake). The Big Sioux River in the northwest corner of the state forms the North/South boundary with South Dakota. To the north lies Minnesota and to the south lies Missouri. There are several natural lakes in the state, most notably Spirit Lake, West Okoboji Lake, and East Okoboji Lake in northwest Iowa (see Iowa Great Lakes).To the east lies Clear Lake, Iowa. Man-made lakes include Lake Odessa,1 Saylorville Lake, Lake Red Rock, Coralville Lake, Lake MacBride and Rathbun Lake.

Iowa's natural vegetation is the Tallgrass prairie and Savanna while the topography of the state is gently rolling plains. Loess hills lie along the western border of the state, some of which are several hundred feet thick. In the northeast, along the Mississippi River, is a section of the Driftless Zone, which in Iowa consists of low rugged hills covered with conifers—a landscape not usually associated with this state.

The point of lowest elevation is Keokuk in southeastern Iowa, at 480 feet (146 m). The point of highest elevation, at 1,670 feet (509 m), is Hawkeye Point, located in a feedlot north of Sibley in northwest Iowa. The mean elevation of the state is 1,099 feet (335 m). Considering the size of the state at 56,271 square miles (145,743 km²), there is very little elevation difference.

Iowa has 99 counties. The state capital, Des Moines, is located in Polk County (#60).

Iowa has the highest average radon concentrations in the nation due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within the state, such as Iowa City have passed requirements for radon resistant construction in all new homes.

Climate

Iowa, like most of the Midwest, has a humid continental climate throughout the state (Koppen climate classification Dfa) with extremes of both heat and cold. The average annual temperature at Des Moines is 50 °F (10 °C); for some locations in the north the figure is under 45 °F (8 °C), while Keokuk, on the Mississippi River, averages 52 °F (12 °C). Winters are brisk and snowfall is common. Spring ushers in the beginning of the severe weather season. Iowa averages about 50 days of thunderstorm activity per year. US Thunderstorm distribution. src.noaa.gov. Last accessed February 13, 2008. Tornadoes are common during the spring and summer months, with an average of 37 tornadoes in a single year.Mean Annual Average Number of Tornadoes 1953–2004. ncdc.noaa.gov. Last accessed November 1, 2006. The Iowa summers are known for heat and humidity, with daytime temperatures often near 90 °F (32 °C) and sometimes exceeding 100 °F (38 °C).