It is hard to imagine today, not knowing what a woman's maiden name was. Some women chose to keep their maiden name or hyphenate their name with their husbands name. Women have only had the right to vote for 100 years and that before that, they were considered their husbands property. When you are property, your maiden name is often lost.
It is bound to happen to you at some point, you are going to be dealing with Mary. She is your ancestor and you have no idea what her last name is. Is this the end of the road, are you doomed to never find her maiden name?
I know you are probably tired of me saying maybe but it isn't always possible to find the name but before you admit that, there are a few things you can try.
First, especially in the south, the mother's maiden name is often used as a fist name. So if you find a child with what obviously could be a last name, you may have hit pay dirt. That Bryant, Montgomery or Tremont may just be your clue.
In England, the middle name is often the clue. I found one of my own ancestors this way. The last last ancestor I knew was Catherine Watson Worn. I found her birth and her father is John Worn and her mother is Mary. After much research I found the marriage of John Worn and Mary Watson.
A will is also a place to find a maiden name but it is more difficult. You need to know which will to look at. You will need to search for hints to the name perhaps in the marriage witnesses or in sponsors at religious ceremonies. In a will fathers often refer to their daughters as Mary, the wife of John Worn or something of this nature so you know that she is the right one.
Look at the neighbors and people living close by. Family often lives near each other.
Cemeteries are also an option. Look for names on stones and also look at the families who are buried around your ancestor. Families will often be buried together or near each other.
If you ancestor remains unknown try to use the information you may have about people they interact with to see who might actually be related. Look at land records, work records just about any piece of information that may relate to this family. You may find the maiden name mentioned in a pension record. Just keep trying until you run out of ideas and then try to think of another idea.
Not all names will reveal themselves. Move on for today and come back another day with new ideas.