If Illinois Split in Two, Where Would the Southwest Suburbs End Up?

What if Illinois split in two and the new state line ran right through the southwest suburbs?

Mokena on one side. Orland Park on the other. Frankfort and Tinley Park caught somewhere in the middle.

So... where would you want to live?

Would your taxes go up? Go down? Would your house suddenly be in Illinois, “New Illinois,” Indiana, or whatever this new place eventually gets called?

And what happens to everything else?

Schools. Roads. Home values. Pensions. Your commute.

It sounds ridiculous.

Except 33 Illinois counties have already voted to explore separating from Cook County, more counties are preparing to vote on the idea, and Indiana even created a commission to study changing its border with Illinois.

So no, Illinois is probably not splitting next week.

But if it ever did?

The southwest suburbs could be one of the strangest places on the map.

We’re Not Chicago. But Are We “Downstate”?

This may be the biggest problem with the whole idea.

The Illinois divide is usually presented as something simple.

Chicago versus Downstate.

Urban versus rural.

Blue versus red.

Then there’s us.

The southwest suburbs don’t fit neatly into any of those boxes.

Mokena and New Lenox sit in Will County.

Frankfort crosses Cook and Will counties.

Tinley Park crosses Cook and Will counties.

Orland Park also reaches across the Cook-Will County line.

So when somebody says, “Just separate Cook County from the rest of Illinois,” it sounds simple until you actually look at where we live.

Around here, that line doesn’t separate skyscrapers from cornfields.

It cuts through the suburbs.

Which raises a much more interesting question:

If somebody really made us choose, which Illinois are we?

Where Would They Even Draw the Line?

Nobody knows.

There is no approved map showing a future Illinois state line running through Tinley Park or Frankfort.

One proposal introduced in the Illinois House calls for the 101 counties outside Cook County to form a new state. Even that proposal leaves open the possibility that some outlying portions of Cook County could choose to join the new state.

The resolution has not advanced and remains far from becoming reality.

But take the simplest version of the idea for a minute.

Cook County stays in the current Illinois.

The rest of the state leaves.

Now look at our area.

New Lenox and Mokena clearly fall on the Will County side.

But Frankfort, Tinley Park and Orland Park immediately create questions because their communities reach across the county line.

Do you split the towns?

Move the state boundary around them?

Let residents decide?

Move the entire community to one side?

Nobody has an answer because nobody is remotely close to having to make that decision.

Still, it shows why yelling “split the state” is a lot easier than figuring out where the new state actually begins.

And What Would We Even Become?

There isn’t one agreed-upon answer to that either.

One movement advocates creating a new state generally referred to as New Illinois.

Indiana has floated another possibility.

In 2025, Indiana lawmakers created the Indiana-Illinois Boundary Adjustment Commission to study whether the border could someday be moved west to include portions of Illinois.

That does not mean Indiana can simply claim Illinois counties. Illinois and the federal government would have to agree to any actual boundary change.

But for the sake of the thought experiment, there are several possibilities.

Stay in Illinois.

Join a newly created state.

Join Indiana.

Or negotiate a completely different map that nobody has drawn yet.

Which brings us to the question most people around here would probably ask first.

Would My Taxes Go Up or Down?

Of course it comes back to taxes.

If Mokena and Orland Park suddenly found themselves in different states, which side would actually cost more to live on?

Would one state have a lower income tax?

Would property taxes change?

Would one side spend less but provide fewer services?

Would another state spend more but tax more?

There is no honest answer today because there is no actual financial plan for a new state.

Anybody telling you exactly what your tax bill would look like is guessing.

There is, however, an older study that makes the whole argument more interesting.

Researchers at Southern Illinois University's Paul Simon Public Policy Institute studied where Illinois state tax dollars were generated and where state money was spent.

The study was published in 2018 using 2013 fiscal data, so these should not be treated as current 2026 numbers.

But the pattern was striking.

Cook County received about 90 cents in state spending for every dollar it generated.

The five suburban collar counties surrounding Cook, including Will County, received about 53 cents.

Southern Illinois received about $2.81.

And that makes the southwest suburbs particularly interesting.

Will County is not rural Southern Illinois.

Mokena and New Lenox are part of the Chicago suburban economy.

So if Will County became part of a new state, that new state would potentially take part of the Chicago-area economic engine with it.

Suddenly this isn’t a clean Chicago-versus-Downstate divorce.

The money gets messy too.

What Happens to Your House?

This is where the whole thing gets especially interesting from a real estate standpoint.

Buyers around here already compare Cook County and Will County.

Taxes matter.

Schools matter.

Commutes matter.

Services matter.

Two homes only a few miles apart can already carry very different costs depending on exactly where they sit.

Now imagine turning that county line into a state line.

Would buyers pay more to stay on one side?

Would lower taxes increase demand somewhere else?

Would schools eventually be funded differently?

Could two nearly identical homes in the same general area suddenly operate under completely different state laws?

Nobody knows which side would come out ahead.

But buyers would absolutely notice.

If you've ever watched someone compare an Orland Park home with one in Mokena because of Cook versus Will County taxes, imagine adding this question:

“What state is the house in?”

That would be a new one.

What About Schools?

This could get complicated quickly too.

Illinois provides state funding to local school districts and establishes rules that affect everything from teacher pensions to education requirements.

If a new state boundary ever cut through this area, school systems would have to be sorted out along with everything else.

Would existing districts stay intact?

Would some districts suddenly operate across state lines?

Would funding change?

Would students on opposite sides of the boundary eventually operate under different state education systems?

Those questions sound far-fetched today.

But they show how much more complicated a state breakup becomes once you stop looking at a statewide map and start looking at actual communities.

Then There’s the Bill Nobody Gets to Walk Away From

Illinois also has financial obligations.

A lot of them.

The state's five retirement systems carried approximately $144.6 billion in unfunded liabilities as of June 30, 2025.

You do not need a pension-accounting degree to understand the problem.

If Illinois somehow became two states, somebody would have to determine how existing obligations were divided.

Cook County?

The new state?

Both?

And how much?

You don't simply draw a line across Illinois and leave the bills sitting on the other side.

History gives us a pretty good example of that.

Yes, America Has Actually Split a State Before

West Virginia used to be part of Virginia.

During the Civil War, the western portion of Virginia separated and became its own state in 1863.

The circumstances were obviously nothing like Illinois today.

Virginia had joined the Confederacy. The country was at war. West Virginia's creation happened under extraordinary circumstances.

But it proves one thing:

A state can be divided.

It also proves the arguments do not end when the line gets drawn.

Virginia and West Virginia spent decades fighting over how much of Virginia's existing debt the new state should assume.

The dispute eventually reached the U.S. Supreme Court.

So if Illinois ever tried something similar, the new border would probably be the beginning of the financial argument, not the end.

Could Illinois Really Split?

Technically, yes.

Practically?

Extremely difficult.

The county votes happening around Illinois are advisory. A county cannot simply vote itself out of the state.

Creating a new state from an existing one would require approval from Illinois and the United States Congress.

Moving counties into Indiana would likewise require agreement far beyond a local referendum.

So nobody is waking up next month and discovering that New Lenox is suddenly located in America's 51st state.

This would require an enormous political agreement that does not currently exist.

Maybe the Bigger Question Is Where We Actually Belong

Forget for a second whether Illinois will ever actually split.

The whole debate exposes something interesting about the southwest suburbs.

Where exactly do we fit?

We're economically connected to Chicago.

We're part of the Chicago metropolitan area.

People commute north, use Chicago-area transportation, work throughout the region and move freely between Cook and Will counties every day.

But we're not Chicago.

And plenty of people around here probably feel culturally or politically closer to communities in Will County than they do to downtown Chicago.

That is what makes the imaginary state line interesting.

From far away, Chicago versus Downstate looks simple.

Zoom into Frankfort, Mokena, New Lenox, Tinley Park and Orland Park and it gets a lot harder.

We're sitting right in the middle.

And if Illinois ever really forced us to pick a side, the answer might not be nearly as obvious as people think.

Common Questions About Illinois Splitting Into Two States