Johnson County is a county in Iowa, United States, about 20 miles southeast of Cedar Rapids. It had a population of 152,854 at the 2020 census, an estimated 160,044 by 2025, and covers 623.06 square miles (1,613.7 km2) centred near 41°40′N 91°35′W.
Iowa City is the county seat and the county’s largest city; its postal code is 52240. The county holds 12 incorporated cities and 12 unincorporated communities across 21 townships, and it runs on Central Time. Its FIPS code is 19103.
Towns & Villages in Johnson County
Johnson County has 24 named places on record: 12 incorporated cities and 12 unincorporated communities and census-designated places with no local government of their own. Iowa’s municipal law has only one class of incorporated place — “city” — so every incorporated town on this list, regardless of size, carries that label. CDP stands for census designated place; Unincorp. covers crossroads and rural communities with no formal boundary.
| Place | Type | Township | Pop. | ZIP |
|---|---|---|---|---|
| Iowa City | City · seat | — | 74,828 | 52240 |
| Coralville | City | — | 22,318 | 52241 |
| North Liberty | City | — | 20,479 | 52317 |
| Tiffin | City | Clear Creek | 4,512 | 52340 |
| Solon | City | — | 3,018 | 52333 |
| West Branch | City | — | 2,509 | — |
| Lone Tree | City | — | 1,357 | 52755 |
| University Heights | City | — | 1,228 | 52246 |
| Swisher | City | — | 914 | 52338 |
| Hills | City | — | 863 | 52235 |
| Shueyville | City | — | 731 | — |
| Oxford | City | Oxford | 722 | 52322 |
| Frytown | CDP | — | — | — |
| Oakdale | Unincorp. | — | — | — |
| Amish | Unincorp. | — | — | — |
| Cosgrove | Unincorp. | — | — | — |
| Morse | Unincorp. | — | — | — |
| Newport | Unincorp. | Newport | — | — |
| Oasis | Unincorp. | — | — | — |
| River Junction | Unincorp. | — | — | — |
| Sharon Center | Unincorp. | Sharon | — | — |
| Sutliff | Unincorp. | — | — | — |
| Twin View Heights | Unincorp. | — | — | — |
| Windham | Unincorp. | — | — | — |
West Branch’s citywide population figure above is mostly a Cedar County number — the bulk of the city sits east of the Johnson County line, and only a western edge of its limits reaches into Johnson County, so its 2,509 residents are overwhelmingly Cedar County residents, not Johnson County ones. University Heights is a separate incorporated city that sits entirely inside Iowa City’s boundaries, an enclave with its own council and police force; it uses Iowa City’s postal codes because it has none of its own.
ZIP Codes
- 52240 — Iowa City (downtown and east side)
- 52245 — Iowa City
- 52246 — Iowa City (also serves University Heights)
- 52242 — Iowa City (University of Iowa campus, a unique single-entity ZIP)
- 52244 — Iowa City (post office box ZIP)
- 52241 — Coralville
- 52317 — North Liberty (also serves Shueyville)
- 52340 — Tiffin
- 52333 — Solon
- 52755 — Lone Tree
- 52338 — Swisher
- 52235 — Hills (post office box ZIP)
- 52322 — Oxford
Frytown, Oakdale, Amish, Cosgrove, Morse, Newport, Oasis, River Junction, Sharon Center, Sutliff, Twin View Heights and Windham have no ZIP code of their own; mail there is delivered under the nearest incorporated town’s code. The Johnson County sliver of West Branch is likewise served by that city’s own 52358 ZIP, which is administered from Cedar County and not counted among Johnson County’s codes.
Geography
Johnson County sits in east-central Iowa on gently rolling glaciated till plains, part of the Iowa River valley. Of its 623.06 square miles, 613.00 are land and 10.07 are water, about 1.6 percent — most of it Coralville Lake, a reservoir on the Iowa River formed by the Coralville Dam just north of Iowa City and Coralville. The Iowa River runs south through the county’s middle, past Iowa City and on toward its junction with the Cedar River east of the county line, and Clear Creek and Old Man’s Creek drain the county’s western half.
Linn County borders Johnson to the north, Cedar County to the east, Muscatine County to the southeast, Louisa County to the south, Washington County to the south and southwest, Iowa County to the west and Benton County to the northwest. Washington County, Louisa County, Cedar County, Muscatine County, Iowa County and Benton County all have their own pages on this site; Linn County does not.
Demographics
Johnson County had a population of 152,854 at the 2020 census, and the latest estimate puts the county near 160,044 residents, making it Iowa’s fourth-most populous county. Iowa City and Coralville are by far the two largest communities, together holding well over half the county’s population. Median household income runs about $74,935, higher than Iowa’s statewide figure of $71,433 under the 2023 ACS. The county has grown steadily more diverse: its White share of the population fell from 95.15 percent in 1980 to 74.90 percent in 2020, while Black or African American residents rose from 1.45 percent to 8.27 percent over the same span.
Economy & Local Life
Educational services employs the most workers in the county, about 17,672 people, followed by health care and social assistance at 16,863 and retail trade at 10,082. The University of Iowa, founded in 1847 and enrolling more than 31,000 students as of fall 2025, anchors both figures directly: it is the county’s largest single employer and its teaching hospital, University of Iowa Hospitals & Clinics, is one of the region’s largest health care employers. Iowa City’s downtown and the Coral Ridge Mall corridor in Coralville carry most of the county’s retail trade. The county’s biggest recurring draw is University of Iowa Hawkeye football at Kinnick Stadium each autumn, which fills Iowa City’s hotels and restaurants on home-game Saturdays well beyond what the city’s own population would support.
History
The Wisconsin Territorial legislature created Johnson County on December 21, 1837, and it was organized on July 4, 1838, the same day Iowa Territory itself came into being. It was originally named for Richard Mentor Johnson, the sitting U.S. vice president. In 2020 the county’s board of supervisors voted unanimously to rededicate the name to Lulu Merle Johnson, an unrelated woman who in 1941 became the first Black woman in Iowa to earn a doctorate; the county’s legal name did not change.
Iowa City served as the capital of Iowa Territory from 1841 to 1846 and then as Iowa’s first state capital from 1846 until the capital moved to Des Moines in 1857. The Old Capitol building from that era still stands on the University of Iowa campus and is a National Historic Landmark. In June 2008, the Iowa River crested at a record flood stage in Iowa City, flooding dozens of University of Iowa buildings and forcing a lengthy, costly campus rebuilding.
Getting There
Interstate 80 crosses the county’s northern edge through Coralville and North Liberty, with Interstate 380 branching south from it into Iowa City. U.S. Highway 6, U.S. Highway 218, Iowa Highway 1, Iowa Highway 27 (the Avenue of the Saints) and Iowa Highway 965 also run through the county.
- Cedar Rapids — about 20 miles north
- Davenport (Quad Cities) — about 60 miles east
- Des Moines — about 110 miles west
- Muscatine — about 30 miles southeast
The Eastern Iowa Airport in Cedar Rapids, about 20 miles north of Iowa City, is the nearest commercial airport. Amtrak does not stop in Johnson County; the nearest station is on the California Zephyr line in Mount Pleasant, about 45 miles south.
Townships
Johnson County is divided into 21 civil townships: Big Grove, Cedar, Clear Creek, East Lucas, Fremont, Graham, Hardin, Jefferson, Liberty, Lincoln, Madison, Monroe, Newport, Oxford, Penn, Pleasant Valley, Scott, Sharon, Union, Washington and West Lucas. The Census Bureau does not publish separate 2020 population counts for Iowa’s minor civil divisions, so no township-by-township breakdown is available here. A handful of townships share their name with a place inside them: Oxford Township takes its name from the city of Oxford, Newport Township contains the unincorporated community of Newport, and Sharon Township contains Sharon Center.
Frequently Asked Questions
Where is Johnson County located?
It sits in east-central Iowa on the Iowa River, about 20 miles southeast of Cedar Rapids, bordered by Linn, Cedar, Muscatine, Louisa, Washington, Iowa and Benton counties.
What is the population of Johnson County?
152,854 at the 2020 census, with an estimate near 160,044 by 2025 — Iowa’s fourth-most populous county.
How big is Johnson County?
623.06 square miles (1,613.7 km2), of which 613.00 square miles are land.
What is the county seat of Johnson County?
Iowa City, home of the University of Iowa, is the county seat and largest city.
How many towns and cities are in Johnson County?
Twelve incorporated cities — Iowa City, Coralville, North Liberty, Tiffin, Solon, West Branch (partly), Lone Tree, University Heights, Swisher, Hills, Shueyville and Oxford — plus twelve unincorporated communities and one census-designated place.
What ZIP codes does Johnson County use?
52240, 52242, 52244, 52245 and 52246 for Iowa City; 52241 for Coralville; 52317 for North Liberty and Shueyville; 52340 for Tiffin; 52333 for Solon; 52755 for Lone Tree; 52338 for Swisher; 52235 for Hills; and 52322 for Oxford.
What is Johnson County known for?
The University of Iowa, founded in 1847 in the county seat, Iowa City, which also served as Iowa’s territorial and state capital from 1841 to 1857.
More counties in this state: Towns and villages in Iowa.