By now, you know that I love the census. I have written before about finding a widow by her maiden name instead of her married name. If you don't find her, what then? Why, look for her children. Look for the marriages of her children. If some of her children were male, they would bear the surname of the father. If some of her children were female, they might be married and so the search for a marriage certificate. You might find the mother living with either one. In the case of the daughter, you might find her listed with the surname of the son-in-law.