I lent money to a man who has since passed away. I have a signed note, which includes a specified interest rate. Isn't his wife responsible for paying this debt?
Whether this fellow's wife is responsible depends on what state the debt was incurred in. In New York and other states that follow marital property rules based on common law property systems -- as opposed to the community property principles followed in California and nearly two handfuls of other states -- only the spouse who racked up the debt in his or her name is responsible for paying it. The only exception is debts for necessities, such as food, clothing, or medical care.
Only if you live in a "community property" state is the deceased debtor's spouse legally responsible for the debt. (See Nolo's article Dividing Property and Debt During Divorce FAQ for a list of community property states.)
No matter where you live, however, you have a claim against the deceased debtor's estate. Find out whether there will be a probate proceeding in which you can request that your debt be paid out of his probate assets.