Robert,

I am enjoying your story and I'm witnessing your biggest challenge - that of being a researcher or being a story teller.

Your opening sentence put me in a visual mode (or mood). I was thinking of the time of day when that momentous event occurred.
I could sense the sweat around the collar and under the arms. So, for the rest of the paragraph I wanted to know what they were thinking or feeling.
You can assume that I (the reader) know something about the relationship between colored men and this particular war. Just tell me about Walker and James.

You could pare down paragraph two by stating that Walker is 25 and his brother James is 18 and still living with his parents. What was Walker probably doing (according to the census) in 1864?
Ex. "When Walker left the small farm in the northen part of the county to tell his father of his decision to join the Union, he was as surprised by both of his parents support as he was of his younger brother wanting to follow suit. Verlinda became haunted by the prospect that she might be seeing her sons for the last time; but she knew that colored men, now given the opportunity, must participate in the fight for their own freedom. If anyone was more frightened than his mother it was Mary Jackson Curry, his wife of five years."
Something like this gets us closer to feeling for Walker, James, Michael, Verlinda and Mary.

Again, assuming that I (the reader) know a little about some of the battles, just tell me of the battles Walker and James (or their respective troops) were in. Did they ever fight on the same day? How far apart were they?

Flesh out the characters, toss in some dates and you got a fascinating story!

Two brothers leaving their families to fight for the freedom of their people - and you have the documents and research to base it in facts - it doesn't get much better than that!
A powerful first sentence. I'm digging your story; I want to read more!

Peace,
"Guided by the Ancestors"
http://geder.wordpress.com