When was Lake County founded?

Lake County was founded in 1839, formed from McHenry County, and named after Lake Michigan.

What is the county seat of Lake County?

The county seat of Lake County is Waukegan.

Is there an online parcel map for Lake County?

Yes. Lake County publishes a parcel map of 278,985 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Lake County's boundary or name changed?

Lake County was created in 1839 from McHenry County. The Atlas of Historical County Boundaries records no boundary change since.

Who issues building permits in Lake County?

The county's page on building permits: Permits. Inside a city or town, ask that city first.

Who issues septic and well permits in Lake County?

The county's page on septic systems and wells: Behavioral Health.

Is my lot in a flood zone?

We do not have flood maps for Lake County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

County · code 17097

Lake CountyIllinois

Lake County is a county in Illinois with its seat in Waukegan. It was formed in 1839 from McHenry County and named after Lake Michigan.

Founded1839
County seatWaukegan
Named forLake Michigan
Land area444 sq mi + 925 sq mi water
Population714,342 2020 Census
Parcels mapped278,985 checked 15 October 2026

Open the free map Click any parcel in Lake County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1839 from McHenry County

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

Lake County was created from McHenry County on March 1, 1839.

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

1839
Lake County created Lake created from McHenry.
from McHenry
1 March 1839 · Ill. Laws 1838-1839, pp. 216-217

Land and parcels

What the maps cover in Lake

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

Parcels Good enough

Lot lines and tax-map numbers for 278,985 parcels from Lake County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 15 October 2026
Address points Missing

No public address points layer found for Lake County yet.
Buildings Reference

Roof outlines traced from aerial imagery from FEMA Response Geospatial Office with Oak Ridge National Laboratory (ORNL). Good for seeing what is on a lot; not accurate enough to set a fence from.
checked 18 October 2026

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

Lake by the Census

Population

714,342 2020 Census count

Housing units

269,378 2020 Census count

Land area

444 square miles

Water area

925 square miles · 68% of the county, including large bodies of water

People per sq mi

1,610 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.

Permits

Health department: septic and well
Behavioral Health
from lakecountyil.gov · checked 13 October 2026
Permitsfrom lakecountyil.gov
Permitsfrom lakecountyil.gov
Water Wellsfrom lakecountyil.gov
Well & Septic Evaluations from lakecountyil.gov

Zoning and code

Planning and zoning
Belvidere Medical Building
from lakecountyil.gov · checked 13 October 2026
Ordinancesfrom lakecountyil.gov
Ordinances & Codesfrom lakecountyil.gov
Zoningfrom lakecountyil.gov
Zoning Mapsfrom lakecountyil.gov

County government

County government
The official website of Lake County.
lakecountyil.gov

See your own lot on these maps

Open Lake 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.

Open the free map no sign-in Pro early access

Questions

Common questions about Lake County

When was Lake County founded?: Lake County was founded in 1839, formed from McHenry County, and named after Lake Michigan.
What is the county seat of Lake County?: The county seat of Lake County is Waukegan.
Is there an online parcel map for Lake County?: Yes. Lake County publishes a parcel map of 278,985 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Lake County's boundary or name changed?: Lake County was created in 1839 from McHenry County. The Atlas of Historical County Boundaries records no boundary change since.
Who issues building permits in Lake County?: The county's page on building permits: Permits. Inside a city or town, ask that city first.
Who issues septic and well permits in Lake County?: The county's page on septic systems and wells: Behavioral Health.
Is my lot in a flood zone?: We do not have flood maps for Lake County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby