List of counties in Iowa

Counties of Iowa
LO SX OA OB DK CY ET PL KH WN HK WT CE MT FD HW CW WH AM CT FT BM BT FN WR HB PT BV CK PM WD IA SA CH WB HM HA GN BH BC DW DB JK JN LN BE TM MR SR BN GR CR CF MN HR SH AB GT DA PK JP PH IW JH CD CN ST MC LA WS KK MK MA WA MD AD CA PW ML MM AA UN CL LC MO WP JF HN DM LE VB DV AN WE DT RN TA PA FM
Location	State of Iowa
Number	99
Populations	3,544 (Adams) – 505,255 (Polk)
Areas	381 square miles (990 km2) (Dickinson) – 973 square miles (2,520 km2) (Kossuth)
Government	County government
Subdivisions	cities, towns, townships, unincorporated communities, census designated place

There are 99 counties in the U.S. state of Iowa. The first two counties, Des Moines County and Dubuque County, were created in 1834 when Iowa was still part of the Michigan Territory. In preparation for Michigan's statehood, part of Michigan Territory was formed into Wisconsin Territory in 1836.^[1] Two years later, the western portion was split off to become Iowa Territory.^[2] The south-eastern part of Iowa Territory became Iowa, the 29th state in the union, on December 28, 1846,^[3] by which point 44 counties had been created. Counties continued to be created by the state government until 1857, when the last county, Humboldt County, was created.^[4] One of the most significant days in Iowa county history was January 15, 1851, on which 49 counties were created.^[5]

The Iowa Constitution of 1857, which is still in effect today, states that counties must have an area of at least 432 square miles (1,120 km²), and no county may be reduced below that size by boundary changes.^[6] However, exceptions to this rule were granted, as ten counties have areas below this size. (The table below shows land area, but the Constitution deals with total area.^[6]) The smallest county (Dickinson) has a land area of 381 sq mi (990 km²), while the largest (Kossuth) has an area 973 sq mi (2,520 km²). Polk County is the most densely populated county at 864/sq mi (333.5/km²), an increase in density from 2010 when it was 655.5/sq mi (253.08/km²).^[7] Polk County contains the state's capital and largest city, Des Moines. In addition, Iowa has one of the smallest percentages of counties whose boundaries are dictated by natural means, the vast majority of which are being formed by lines of survey instead, resulting in many "box counties".