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County tax profile · 2026 · Census ACS + IRS data

Property Tax & Income in Mercer County, Illinois

Mercer County has an effective property tax rate of 1.96%. On the median home value of $146,700, that's roughly $2,878 per year. Median household income is $74,182.

Effective Property Tax Rate1
1.96%
median tax $2,878 ÷ median home $146,700
Median Home Value1
$146,700
owner-occupied
Median Household Income1
$74,182
per-capita $39,391
Est. Annual Tax on Median Home1
$2,878
at 1.96% effective rate

What you'll pay, at a glance

Property taxes are the largest local tax most homeowners pay. The effective rate measures the real tax bill as a share of home value — a more useful number than the nominal “mill rate,” because assessment practices vary county to county.

MetricMercer CountyIllinois (state context)
Effective property tax rate11.96%1.80%
Median home value1$146,700—
State income tax3top rate 4.95%top rate 4.95%
State sales tax38.98% combined8.98% combined

How this is calculated

The effective property tax rate is the median real-estate tax bill divided by the median home value — both for owner-occupied homes, from the U.S. Census Bureau's American Community Survey (ACS 5-year estimates)1. Median income is also from the ACS1. Federal and state income-tax figures use IRS2 and Tax Foundation3 data.

About Mercer County, IL

Mercer County's effective property tax rate of 1.962% sits above Illinois's statewide median of 1.804%, placing it 35th among the state's 102 counties. That ranking puts it in the upper-middle tier of Illinois counties, though the gap with the state figure is narrow. The contrast with the national median of 0.794% is far sharper — this county's rate is more than double the countrywide figure, a reminder of how heavily Illinois relies on property taxes compared with most other states. On a median home value of $146,700, that rate yields an annual tax bill of $2,878. With median household income at $74,182 and per-capita income at $39,391, the levy equates to roughly 3.9% of household earnings. Aledo, the county seat and largest of its communities, anchors a county where homeowners face costs well above what most Americans pay.

Frequently asked questions

What is the property tax rate in Mercer County, IL?
The effective rate is 1.96% — meaning the median tax bill equals about 1.96% of the median home value.
How much are property taxes on a median home?
On the median home ($146,700), the estimated annual bill is about $2,878.
Is Mercer County's rate high or low?
Compare it to the state median of 1.80% and the national average near 1.1%.
How does the effective rate differ from my mill rate?
A mill rate is the nominal levy per $1,000 of assessed value. The effective rate reflects what you actually pay after exemptions and assessments — it's the median tax bill as a share of median home value, so it better predicts your real cost.
Will a reassessment raise my tax bill?
Not necessarily. If your home's assessed value rises, your bill can go up, but only if the mill rate and exemptions stay flat. Contact the Mercer County assessor's office to review your current assessment.
Can I appeal my property tax assessment?
Yes. Most counties allow an appeal when you believe the assessed value exceeds the market value. File with the Mercer County assessor within the local deadline, typically with comparable sales as evidence.
Sources
[1] U.S. Census Bureau — ACS 5-Year (2023) — Median home value (B25077), median real-estate taxes (B25103), median household income (B19013), per-capita income (B19301).
[2] IRS — Statistics of Income — County income, AGI, and real-estate taxes paid.
[3] Tax Foundation — State income, sales, corporate, and estate/inheritance tax rates.