Where is Grundy County?

4 Grundy Counties in 4 states · 90,273 people (2025)

There are 4 counties named Grundy County in the United States, in Illinois, Iowa, Missouri and Tennessee. The most populous is Grundy County, Illinois (county seat: Morris), with 54,052 people in 2025. 4 of them are named after Felix Grundy, American politician (1777-1840).

Map of the United States showing where all 4 Grundy Counties are, labeled by state
Every Grundy County in the United States (red), labeled with its state. Boundaries: U.S. Census Bureau, 2025. Free to use with attribution (CC BY 4.0).

All 4 Grundy Counties

Sorted by state. Each link opens the county's map.

StateCounty seatPopulation 2025Land area (sq mi)EstablishedNamed after
Grundy County, IllinoisMorris54,0524181841Felix Grundy
Grundy County, IowaGrundy Center12,3615021851Felix Grundy
Grundy County, MissouriTrenton9,7444351839Felix Grundy
Grundy County, TennesseeAltamont14,1163601844Felix Grundy

Questions about Grundy Counties

How many Grundy Counties are there?

There are 4 Grundy Counties in the United States, in Illinois, Iowa, Missouri and Tennessee.

Which Grundy County is the largest?

By population, Grundy County, Illinois (54,052 people in 2025). By land area, Grundy County, Iowa (502 sq mi).

Which Grundy County is the oldest?

Grundy County, Missouri, established in 1839. The newest is Grundy County, Iowa (1851).

Why are there so many Grundy Counties?

4 of the 4 are named after Felix Grundy, American politician (1777-1840). Many counties took their names from the same founders, presidents and generals as new states were organized.

How do I find out which Grundy County an address is in?

Open the county map of the state: it has a search box for cities, towns and ZIP codes. On a phone, the "what county am I in" tool on our sister site uses your location.

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Other common county names