Your grandfather left you an inheritance. The two of you were always very close, and it means a lot to you that he left that money in your name. If you're married, what you do next could have a huge impact on the future of that inheritance if your marriage ever ends.
After all, your grandfather clearly wanted you to have it. He would not be pleased to find out that your ex got half and then left the state to marry someone else. That's not why he set that money aside or specifically left it in your name.
To make sure his actual wishes are followed, do not commingle your inheritance with other assets you and your spouse own. Keep it separate. If you need to, open up a new bank account or investment account for the money. Do not use the same account that your spouse shares with you.
The problem is that commingled assets often count as marital assets, which are owned by both of you and therefore need to be split up in the divorce. If you let your spouse have free reign to use that money while you're married, he or she can argue that it is as much his or hers as it is yours.
If you keep it separate, though, you show that you and your spouse both considered that money to be yours all along. That helps it count as separate property during the divorce, and it doesn't need to get divided at all. It stays separate from the rest of your marital estate and remains with you.
It's very important that you understand all of your legal options and the potential ramifications of every action you take, even long before the divorce process begins.
Source: Forbes, "Divorcing Women: Here's How to Protect Your Inheritances And Gifts," Jeff Landers, accessed March 30, 2018