Iowa Geography

The Mississippi River forms the eastern boundary of the state. The boundary along the west is formed by the Missouri River south of Sioux City and by the Big Sioux River north of Sioux City. 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). Man-made lakes include Lake Odessa[1], Saylorville Lake, Lake Red Rock, Coralville Lake, Lake MacBride and Rathbun Lake.

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 http://www.cheec.uiowa.edu/misc/radon.html. Because of the high surface area of the ground rock, radon is free to off-gas from the soils. Many cities within the state, such as Iowa City have passed requirements for radon resistant construction in all new homes.

Areas controlled and protected by the National Park Service include:

• Effigy Mounds National Monument near Harpers Ferry
• Herbert Hoover National Historical Site in West Branch
• Lewis & Clark National Historic Trail
• Mormon Pioneer National Historic Trail

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, the capital (Des Moines) receiving an average of 36.3 inches (92 cm) per season. Spring ushers in the beginning of the severe weather season, as well as bringing increased precipitation and warming temperatures. The Iowan summer is known for heat and humidity, with daytime temperatures often near 90 °F (32 °C) and sometimes exceeding 100 °F (38 °C).

Iowa averages about 50 days of thunderstorm activity per year.[2] Some of these thunderstorms can be severe with high winds and hail. The state has a moderately high risk of tornadic activity with, on average, 37 tornadoes per year, mostly in the spring and summer months.[3]

Iowa is neighbored by the following states:

• Illinois (East of Iowa)
• Minnesota (North of Iowa)
• Missouri (South of Iowa)
• Nebraska (West of Iowa)
• South Dakota (Northwest of Iowa)
• Wisconsin (Northeast of Iowa)