I have a small amount of information regarding Blackwell from a research project published in 1980 by the Youth Community Conservation Improvement Program and funded by a grant through NEWCAP. The information is a bit confusing... it states that Blackwell was named after a man who established a small mill on the Rat River not far from the present site of the town. This was in 1904. It says that no one knows the exact date thta Mr. Flanner arrived, but to be between 1904-1909.
So it's a bit confusing because this man's name was not Blackwell. If you would like further information from this research project, please email me.
Sorry I couldn't be of more help.