What county is Sandwich, IL in?
The Sandwich IL county answer is mostly DeKalb County, with the eastern edge of the city in Kendall County. The City of Sandwich also lists LaSalle County on its own website, and the Lake Holiday area just south of town, which many people call Sandwich, sits in LaSalle County. The county decides who assesses the home, when the tax bill is due, and which office records your deed.
By Kealan O’Neil | November 2, 2026
Sandwich sits at the far southwest edge of Chicago’s Western Suburbs, right where DeKalb, Kendall, and LaSalle Counties meet. It’s one of the places people start looking when they want more house for the money and don’t mind a longer drive to Aurora or Naperville.
Most buyers don’t think about the county until a tax bill or an assessor’s letter shows up. In a Sandwich search, though, two homes a few miles apart can answer to three different county offices, and that’s worth knowing before you fall for one.
This guide walks through the Sandwich IL county split, what changes from one side of the line to the other, and a simple way to confirm the county for any address. If you’re new to the area, our Sandwich, IL homes and market guide is a good place to start.
How the Sandwich IL county line actually works
The City of Sandwich’s comprehensive plan describes the city as sitting in Sandwich Township in DeKalb County, extending past the county line into Kendall County, with its southern boundary on the LaSalle County line. In plain terms, most addresses inside city limits are DeKalb County addresses.
The Kendall County piece is on the east side. Little Rock Township, the Kendall County township that includes all of Plano, says on its own website that it also covers a portion of Sandwich, specifically the eastern edge of the city.
Where LaSalle County comes in
South of town, the picture changes again. Lake Holiday is a private community built around a 328-acre man-made lake between Sandwich and Somonauk, and its property owners’ association places it in LaSalle County.
That matters because a Lake Holiday home can carry a Sandwich or Somonauk mailing address while being outside Sandwich city limits and in a different county entirely. The ZIP code on a listing tells you which post office delivers the mail. It doesn’t tell you which county taxes the house.
City limits are a separate question
County and city are two different layers. A home can be in DeKalb County and inside Sandwich city limits, or in DeKalb County on unincorporated land just outside town, with county zoning and often a private well and septic system.
The line also moves.
In June 2026 the City Council annexed 422 W. Church Street and zoned it M-2 General Manufacturing, and in July 2026 the council held a first reading on annexing 903 W. Center Street and rezoning it from A-1 agricultural to R-1 residential. Land at the edge of town can change hands from county rules to city rules, so check the current status of anything near the boundary.
If you’ve looked at Millington, you’ll see a similar setup. Our Millington two-county checklist covers a similar Kendall and LaSalle split a few miles east.
What changes from one side of the line to the other
The house might look the same on either side, but the paperwork doesn’t. Here’s what follows the Sandwich IL county line.
Who assesses the home
In DeKalb County, the first stop is the township assessor.
The DeKalb County Assessment Office lists Sandwich Township’s assessor with an office at 201 W. Center Street in Sandwich, and Somonauk Township has its own assessor. On the Kendall side, Little Rock Township runs its assessor’s office out of Plano.
Lake Holiday homes go through LaSalle County’s assessment system. If you ever want to question an assessed value, the deadlines and the board of review are set by the county the home is in, not by the town on the mailing address.
When the tax bill is due
Illinois property taxes are paid a year behind, and each county sets its own calendar, so the Sandwich IL county your home sits in decides when you pay. For 2025 taxes paid in 2026, here’s how the three counties compared:
- DeKalb County: bills mailed May 1, 2026, with installments due June 3 and September 3, 2026, according to the DeKalb County Treasurer’s billing FAQ.
- Kendall County: installments due June 9 and September 9, 2026, per the Kendall County Treasurer.
- LaSalle County: installments due July 15 and September 9, 2026, per the LaSalle County Treasurer’s collection schedule.
DeKalb County notes that late payments pick up a 1.5% penalty the day after the due date and another 1.5% each month after that. If you buy a home and the bill still shows the prior owner’s name, the treasurer’s office says to download a duplicate and check your closing papers to see who owes it.
Homestead exemption basics
The general homestead exemption follows state law in all three counties. Under 35 ILCS 200/15-175, the maximum reduction is $6,000 of equalized assessed value in counties outside Cook and the counties that border it, which includes DeKalb, Kendall, and LaSalle.
The same statute says that when a homestead is sold, the exemption stays in place for the rest of that assessment year. After that, the assessor can require the new owner to apply, so ask the township assessor what your county needs from you after closing.
Deeds, permits, and the county clerk
Your deed is recorded in the county where the property sits. Unincorporated homes also get building permits, zoning answers, and well and septic oversight from the county, while homes in city limits go through Sandwich City Hall at 144 E. Railroad Street.
Older Sandwich homes and city water
If the home is inside city limits, it’s likely on City of Sandwich water and sewer. The City bills water and sewer quarterly, and its FAQ says a 20% late penalty applies when the full payment isn’t received by the due date.
One detail people miss: the City offers an optional second meter for outdoor water use, so lawn and garden water isn’t charged for sewer. The City lists the cost at $375 for the meter plus $75 for the plumbing inspection.
Lead service lines near the city’s core
The City of Sandwich water FAQ says lead isn’t present in the city’s groundwater source or its treated water. The risk is in the pipe that runs to the house, and the City notes lead was used locally until 1960, so a home built before then may have a lead service line.
The City’s April 2024 lead service line plan counted 61 known lead lines and 171 suspected lead lines, mostly near the core of town. The homeowner owns and maintains the portion of the line inside the property boundary.
Paying for replacement is still being worked out. In June 2026 the City Council voted 3 to 2 against a proposed 50/50 cost-sharing agreement with owners, and at the July 6, 2026 meeting the council discussed an estimated 236 known lead lines at roughly $15,000 each and talked about grant funding and a bid package. Under state law, the City’s final replacement plan is due to the Illinois EPA by April 15, 2027.
For an older house, ask the seller what the service line is made of and request a look where the line enters the basement. Our guide to lead service lines in Aurora walks through what that check looks like in practice.
How to confirm the Sandwich IL county for any address
You don’t have to guess. These five steps take a few minutes and work for any listing in the 60548 area.
- Read the parcel number. Kendall County parcel numbers begin with a township code, and Little Rock Township parcels start with 01. A DeKalb or LaSalle parcel number uses its own county format.
- Look the parcel up on the county site. Search the address in the DeKalb, Kendall, or LaSalle County property tax inquiry and confirm the county, township, and tax code that come back.
- Pull the last tax bill. The bill shows the county, the township, every taxing body, and the exemptions the current owner receives.
- Confirm city limits. Ask the City of Sandwich whether the address is inside city limits, on city water and sewer, or on a private well and septic system.
- Check for an association. If the home is at Lake Holiday or in a subdivision with an association, ask for the current assessments, rules, and any steps the association requires before closing.
Sandwich county questions buyers ask first
Is Sandwich, IL in DeKalb County or Kendall County?
Is Lake Holiday part of Sandwich?
Does the county change my property tax due dates?
Do older homes in Sandwich have lead water lines?
How do I choose a real estate agent in Sandwich, IL?
Getting the county right before you commit
The Sandwich IL county question sounds like trivia, but it shapes your tax calendar, your assessor, and who you call when something needs a permit. Sorting it out early keeps the surprises small.
If you’re just starting to look around Sandwich, Plano, or Lake Holiday, I’m happy to pull the parcel records and talk through what each side of the line means for you, no pressure. Call or text Kealan at 630-425-8815.
About Kealan O’Neil
Kealan O’Neil is the Designated Managing Broker and founder of O’Neil Property Group, an independent real estate brokerage based in Yorkville, Illinois. He and his team help buyers and sellers in Yorkville, Oswego, Montgomery, and the surrounding Kendall and Kane County communities, and he owns and manages a local rental portfolio, so he approaches every decision as both a broker and an investor. Call or text Kealan at 630-425-8815.
This post is general information about real estate in the Fox Valley, not legal, tax, or financial advice. Real estate laws, tax rules, and municipal ordinances change, and how they apply depends on your specific situation. Talk with a licensed attorney, CPA, or lender before making decisions about a purchase, sale, or tax matter. O’Neil Property Group is a licensed Illinois real estate brokerage.