When was Hamilton County founded?

Hamilton County was founded in 1857, formed from Webster County, and named after William W. Hamilton.

What is the county seat of Hamilton County?

The county seat of Hamilton County is Webster City.

Is there an online parcel map for Hamilton County?

Yes. Hamilton County publishes a parcel map of 19,286 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.

Has Hamilton County's boundary or name changed?

Hamilton County was created in 1857 from Webster County. The Atlas of Historical County Boundaries records no boundary change since.

Is my lot in a flood zone?

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

County · code 19079

Hamilton CountyIowa

Hamilton County is a county in Iowa with its seat in Webster City, formed in 1857 from Webster County.

Founded1857
County seatWebster City
Named forWilliam W. Hamilton
Land area577 sq mi + 0.8 sq mi water
Population15,039 2020 Census
Parcels mapped19,286 checked 16 October 2026

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

Updated 19 October 2026

Census outline · seat marked

History

Formed in 1857 from Webster County

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

Hamilton County was created on January 8, 1857, from Webster County and named after William W. Hamilton.

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

1857
Hamilton County created Hamilton created from Webster.
from Webster
8 January 1857 · Iowa Acts 1856-1857, ch. 15, secs. 1, 9/pp. 11-13

Land and parcels

What the maps cover in Hamilton

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

Parcels Good enough

Lot lines and tax-map numbers for 19,286 parcels from Hamilton County. Drawn for tax purposes: usually within a few feet of a survey, but not a survey.
checked 16 October 2026
Address points Missing

No public address points layer found for Hamilton 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

Hamilton by the Census

Population

15,039 2020 Census count

Housing units

7,037 2020 Census count

Land area

577 square miles

Water area

0.8 square miles

People per sq mi

26 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

Hamilton County's official site

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

County government

County government
The official website of Hamilton County.
hamiltoncounty.org

See your own lot on these maps

Open Hamilton 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 Hamilton County

When was Hamilton County founded?: Hamilton County was founded in 1857, formed from Webster County, and named after William W. Hamilton.
What is the county seat of Hamilton County?: The county seat of Hamilton County is Webster City.
Is there an online parcel map for Hamilton County?: Yes. Hamilton County publishes a parcel map of 19,286 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Hamilton County's boundary or name changed?: Hamilton County was created in 1857 from Webster County. The Atlas of Historical County Boundaries records no boundary change since.
Is my lot in a flood zone?: We do not have flood maps for Hamilton County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby