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County · code 17161

Rock Island CountyIllinois

Rock Island County is a county in Illinois with its seat in Rock Island. The county was formed on February 9, 1831.

  • Founded1831
  • County seatRock Island
  • Named forRock Island Arsenal
  • Land area428 sq mi + 24 sq mi water
  • Population144,672 2020 Census
  • Parcels mapped65,946 checked 15 October 2026
Open the free map Click any parcel in Rock Island County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

Scott, IAMercerClinton, IAHenryMuscatine, IAWhitesideLouisa, IA Rock Island Census outline · seat marked

Where it is

Rock Island on the map of Illinois

Illinois has 102 counties and county equivalents, each with its own records office. Shapes with a page are links.

Adams CountyAlexander CountyBond CountyBoone CountyBrown CountyBureau CountyCalhoun CountyCarroll CountyCass CountyChampaign CountyChristian CountyClark CountyClay CountyClinton CountyColes CountyCook CountyCrawford CountyCumberland CountyDeKalb CountyDe Witt CountyDouglas CountyDuPage CountyEdgar CountyEdwards CountyEffingham CountyFayette CountyFord CountyFranklin CountyFulton CountyGallatin CountyGreene CountyGrundy CountyHamilton CountyHancock CountyHardin CountyHenderson CountyHenry CountyIroquois CountyJackson CountyJasper CountyJefferson CountyJersey CountyJo Daviess CountyJohnson CountyKane CountyKankakee CountyKendall CountyKnox CountyLake CountyLaSalle CountyLawrence CountyLee CountyLivingston CountyLogan CountyMcDonough CountyMcHenry CountyMcLean CountyMacon CountyMacoupin CountyMadison CountyMarion CountyMarshall CountyMason CountyMassac CountyMenard CountyMercer CountyMonroe CountyMontgomery CountyMorgan CountyMoultrie CountyOgle CountyPeoria CountyPerry CountyPiatt CountyPike CountyPope CountyPulaski CountyPutnam CountyRandolph CountyRichland CountySt. Clair CountySaline CountySangamon CountySchuyler CountyScott CountyShelby CountyStark CountyStephenson CountyTazewell CountyUnion CountyVermilion CountyWabash CountyWarren CountyWashington CountyWayne CountyWhite CountyWhiteside CountyWill CountyWilliamson CountyWinnebago CountyWoodford CountyRock Island County Rock Island
Counties of Illinois · Rock Island highlighted

History

Formed in 1831 from Jo Daviess County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Rock Island County was created from Jo Daviess County, initially without full organization and attached to Jo Daviess for all judicial and other county purposes. The county was fully organized and detached from Jo Daviess on March 1, 1833. Rock Island County exchanged territory with Whiteside County in 1854, an exchange that was later repealed in 1869.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries.

  1. 1831
    Rock Island County created Rock Island created from Jo Daviess; Rock Island not fully organized, attached to Jo Daviess "for all judicial and other county purposes."
    from Jo Daviess
    · Ill. Laws 1830-1831, pp. 52-53
  2. 1833
    Changed Rock Island fully organized, detached from Jo Daviess.
    Jo Daviess
    · Ill. Laws 1832-1833, priv., pp. 17-18
  3. 1849
    Changed Legislature authorized Rock Island to gain from Mercer township 15 north, ranges 1 and 2 west, dependent on local referendum that failed (no change).
    Mercer
    · Ill. Laws 1849, 1st sess., gen., pp. 51-52
  4. 1854
    Exchanged territory Rock Island exchanged with Whiteside.
    with Whiteside
    · Ill. Laws 1853, priv., p. 462; Ill. Laws 1854, priv., pp. 161-162
  5. 1869
    Exchanged territory Rock Island exchanged with Whiteside (repealed act of 4 March 1854).
    with Whiteside
    · Ill. Laws 1869, pub., pp. 94-95, 161

Land and parcels

What the maps cover in Rock Island

Who publishes each layer, how good it is, and when we last checked.

Official
from the office that keeps the record
Good enough
a reliable statewide or national copy
Fallback
a guide only; check the official record
Missing
nothing public found yet

People and land

Rock Island by the Census

Population
144,672 2020 Census count
Housing units
66,729 2020 Census count
Land area
428 square miles
Water area
24 square miles
People per sq mi
338 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Rock Island County's official site

We have found the county's site but not its offices yet; start there.

County government

See your own lot on these maps

Open Rock Island County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

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Questions

Common questions about Rock Island County

When was Rock Island County founded?
Rock Island County was founded in 1831, formed from Jo Daviess County, and named after Rock Island Arsenal.
What is the county seat of Rock Island County?
The county seat of Rock Island County is Rock Island.
Is there an online parcel map for Rock Island County?
Yes. A public source publishes a parcel map of 65,946 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Rock Island County's boundary or name changed?
Rock Island County was created in 1831 from Jo Daviess County. Since then the Atlas of Historical County Boundaries records 3 later changes, chiefly involving Whiteside County and Jo Daviess County.
Is my lot in a flood zone?
We do not have flood maps for Rock Island County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby

Counties next door