http://home.comcast.net/~benningsbrigade/History.htm
It is neither brief nor complete, but it is online and it is free.
Most of what is there will be redone - I have loads of new information, some of which require changes to keep things factual. But as I said this version is free. The "real" version I hope to eventually publish is at August 5, 1862
Best Regards,
Andrew Johnson