The Blackwells (Daddy's Side)

My grandfather's middle name is Ross. This is because his mother's maiden name was Ross. She was Sibyl Clarissa Ross (b. 1884). Her father was James Alexander "Alex" Ross and her mother was Mary L. Blackwell.

That's where I hit a dead end. I don't know who Mary L. Blackwell's parents were. It's been a while since I researched this family and I've had lots of luck on other families since I tried finding out info about them.

I talked to my grandfather today about what he can remember and this is what he had to say:

• Dick Blackwell was Sibyl Clarissa Ross' uncle. He was worth a lot of money, but he disappeared. They thought he might have been taken by outlaws for his money. He homesteaded in Oklahoma and supposedly the city of Blackwell, OK was named after him.
• He recalls an Aunt with the last name of French (One of Mary Blackwell's sisters who married someone named "French")
• I suspect Mary L. Blackwell's father's name was S. J. Blackwell, but I am not sure.

Any help with the Blackwell family research would be most appreciated. My email address is nkiblueeyes@yahoo.com. Thanks!