Back story ... about 10 years ago my MIL inherited somewhere between $250K and $500K from her mom.  A year ago my MIL walks out on my FIL after about 40 years of marriage.  She's initiated divorce proceedings but after a year for whatever reason isn't pushing it very hard.  They've got lawyers, had their property appraised, have more court dates coming up.  Everything we've been hearing is that her inheritance is off the table when it comes to splitting up their assets and determining any spousal support.  My FIL is worried he's going to be poor because all their cash is basically tied up in property and cars and that he'll end up paying spousal support and not have the money to do so.  I find it hard to believe that she gets to keep the entire inheritance after this many years.  This is Wisconsin, as I'm sure things vary by state.

The whole thing is pissing a lot of us off as she seems more set on extracting revenge than ejecting from a marriage that she says she can be in even one more day.  All the while she still sucks money out of the company checking, has the company pay for her car insurance and gas, and works for cash 5 days a week.  I wish my FIL would play hardball, but he doesn't want to 'set her off' since she's very vindictive and can get physical.  I could fill about 3 more paragraphs of shit that has happened but even saying this much is probably more than I should have.

Google says...

Generally, inheritances are not subject to equitable distribution because, by law, inheritances are not considered marital property. Instead, inheritances are treated as separate property belonging to the person who received the inheritance, and therefore may not be divided between the parties in a divorce.
Inheritance and Divorce - FindLaw
family.findlaw.com/divorce/inheritance-and-divorce.html

ETA: not a real lawyer.

Every State is different .
However if said Inheritance $$$$ was put into a joint bank account someone is screwed

Both of my parents died after my wife and I split but before we filed for divorce. She wasn't able to touch a cent. This was in NY.

Pretty much this. If put in a joint account then it is up to the judge how to spread it out. If she is smart she will let the soon to be ex-husband take all the property and keep the inheritance. Would work out better for her. Else if it a communal state like Texas everything she has had since been married can be split 50/50.

depends on who exactly it was willed to and if it was comingled.

In Florida what is yours before the marriage is yours when you leave. What you acquire while you are married is split 50/50. With a few exceptions. Inheritance is one of them. Anything you inherit is not "Marital" property. It is yours when you leave.

I learned this from my lawyer when I got a divorce.

This is your answer. Ohio if kept separate it is separate . IN it auto becomes joint. Put in joint account and it is joint.