If I received the inheritance before I got married, then it’s clearly mine, right?
You should place the inheritance into an account in solely your name and keep the funds in that account separate from all marital funds. If you deposit any marital funds into that account, you could change the separate inheritance funds into marital funds. This includes marital funds that you might mistakenly believe to be separate funds, such as a paycheck.
For example: the husband has a money market account, which he has bought and sold securities through for the past ten years. Recently he marries and after a few months the checking account that he and his wife set up began to accumulate quite a bit of money. At this point the husband decides to deposit some of that money into his separate brokerage account, rather than opening a new one in both of their names. By doing this he is potentially making all the funds in the brokerage account marital, not just that which was saved and deposited during the marriage.
In addition, if you use any part of the inheritance to pay a marital debt or expense, that part has clearly become marital property. In some states, if you replace the paid-out funds with other funds, the account becomes marital property. In other states, the mere act of paying a marital expense with part of a separate fund will turn the entire separate property into marital property.