I am also a descendent of James Halbert Blackwell. He was married before Nancy Barnes to Louisa Ramsey. They were married 3/05/1840 in Crawford County, she died in 1844 in Crawford County. They had two children.
1. William Blackwell b. 1842
2. Mary Ann Blackwell b. 1843
He then married Nancy Barnes 5/02/1847 in Crawford County, MO. And they had 9 children together.