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County · code 17099

LaSalle CountyIllinois

LaSalle County is a county in Illinois, founded in 1831, with its seat at Ottawa.

  • Founded1831
  • County seatOttawa
  • Named forRené-Robert Cavelier, Sieur de La Salle
  • Land area1,135 sq mi + 13 sq mi water
  • Population109,658 2020 Census
  • Parcels mapped72,236 checked 16 October 2026
Open the free map Click any parcel in LaSalle County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

PutnamGrundyKendallMarshallLivingstonDeKalbLeeWoodfordBureau Ottawa Census outline · seat marked

Where it is

LaSalle 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 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 CountyRock Island CountySt. Clair CountySaline CountySangamon CountySchuyler CountyScott CountyShelby CountyStark CountyStephenson CountyTazewell CountyUnion CountyVermilion CountyWabash CountyWarren CountyWashington CountyWayne CountyWhite CountyWhiteside CountyWill CountyWilliamson CountyWinnebago CountyWoodford CountyLaSalle County LaSalle
Counties of Illinois · LaSalle highlighted

History

Formed in 1831 from Putnam County, Vermilion County and Tazewell County

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

LaSalle County was created from Putnam, with parts of Putnam attached to Vermilion and Tazewell counties. Over the following decades, LaSalle County lost territory to the creation of multiple new counties: Kane, McHenry, Ogle, Winnebago, Livingston, Grundy, Kendall, and Marshall, as well as to Marshall through direct transfer.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

  1. 1831
    LaSalle County created La Salle created from Putnam, Non-County Area 4 attached to Vermilion, and Non-County Area 6 attached to Tazewell. Part of Putnam became Non-County Area 8 and was attached to La Salle for administrative and judicial purposes.
    from Putnamfrom Vermilionfrom Tazewell
    · Ill. Laws 1830-1831, pp. 54-57, 62-63
  2. 1836
    Lost territory La Salle lost most of attached Non-County Area 8 to creation of Kane, McHenry, Ogle, and Winnebago. Non-County Area 8 effectively detached from La Salle.
    to Kaneto McHenryto Ogleto Winnebago
    · Ill. Laws 1835-1836, pp. 273-278
  3. 1837
    Lost territory La Salle lost to creation of Livingston.
    to Livingston
    · Ill. Laws 1836-1837, pp. 83-85
  4. 1841
    Lost territory La Salle lost to creation of Grundy.
    to Grundy
    · Ill. Laws 1840-1841, pp. 74-75
  5. 1841
    Lost territory La Salle lost to creation of Kendall.
    to Kendall
    · Ill. Laws 1840-1841, pp. 75-77
Show all 8 changes (3 more, mostly small adjustments)
  1. 1831
    LaSalle County created La Salle created from Putnam, Non-County Area 4 attached to Vermilion, and Non-County Area 6 attached to Tazewell. Part of Putnam became Non-County Area 8 and was attached to La Salle for administrative and judicial purposes.
    from Putnamfrom Vermilionfrom Tazewell
    · Ill. Laws 1830-1831, pp. 54-57, 62-63
  2. 1836
    Lost territory La Salle lost most of attached Non-County Area 8 to creation of Kane, McHenry, Ogle, and Winnebago. Non-County Area 8 effectively detached from La Salle.
    to Kaneto McHenryto Ogleto Winnebago
    · Ill. Laws 1835-1836, pp. 273-278
  3. 1837
    Lost territory La Salle lost to creation of Livingston.
    to Livingston
    · Ill. Laws 1836-1837, pp. 83-85
  4. 1839
    Changed Legislature authorized Marshall and Putnam to gain from La Salle townships 29 to 32, and township 33 south of the Big Vermilion River, range 1 east, dependent on local referendum that failed (no change).
    MarshallPutnam
    · Ill. Laws 1838-1839, p. 241
  5. 1841
    Lost territory La Salle lost to creation of Grundy.
    to Grundy
    · Ill. Laws 1840-1841, pp. 74-75
  6. 1841
    Lost territory La Salle lost to creation of Kendall.
    to Kendall
    · Ill. Laws 1840-1841, pp. 75-77
  7. 1843
    Lost territory La Salle lost to Marshall.
    to Marshall
    · Ill. Laws 1842-1843, pp. 93-94
  8. 1851
    Changed Legislature authorized Putnam to gain from La Salle townships 31 and 32 north, range 1 east, dependent on local referendum that failed (no change).
    Putnam
    · Ill. Laws 1851, gen., pp. 111-112

Land and parcels

What the maps cover in LaSalle

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

LaSalle by the Census

Population
109,658 2020 Census count
Housing units
49,812 2020 Census count
Land area
1,135 square miles
Water area
13 square miles
People per sq mi
97 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

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

Inside a city or town, permits usually come from that city rather than the county.

Records

Permits

Zoning and code

County government

See your own lot on these maps

Open LaSalle 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 LaSalle County

When was LaSalle County founded?
LaSalle County was founded in 1831, formed from Putnam County, Vermilion County and Tazewell County, and named after René-Robert Cavelier, Sieur de La Salle.
What is the county seat of LaSalle County?
The county seat of LaSalle County is Ottawa.
Is there an online parcel map for LaSalle County?
Yes. LaSalle County publishes a parcel map of 72,236 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has LaSalle County's boundary or name changed?
LaSalle County was created in 1831 from Putnam County, Vermilion County and Tazewell County. Since then the Atlas of Historical County Boundaries records 5 later changes, chiefly involving Grundy County, Kane County and Kendall County.
Who issues building permits in LaSalle County?
The county's page on building permits: Permits & Applications. Inside a city or town, ask that city first.
Who issues septic and well permits in LaSalle County?
The county's page on septic systems and wells: School Health Services.
Is my lot in a flood zone?
We do not have flood maps for LaSalle 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