In most states inheritances are protected differently than marital assets, in cases of divorce. However, should you choose to keep such a assets separate because of that, you might find your likelihood of testing that law is somewhat increased...
(ETA: I think even if you co-mingle it, the original inheritance would still have the same protection, but it would be a trickier paper trail. I'm not sure if "growth" accrued on an inheritance is also protected, co-mingled or not, so this might be something you want to some really detailed research if you're leaning one way or the other for any reason, either to protect your inheritance, or to object to your partner's keeping separate).