Thanks Bryan. I feel kind of stupid not looking closer at the regimental history, which of course confirms what you said about them not being at Arkansas Post. I spent some time looking at the Camp Douglas records on familysearch.org and have no idea who this "W. D. Stewart" might be, or where from.

Sorry to trouble you any further, but would you happen to know if there were any William - or other - Stewarts in the Bright Star Rifles or other companies from Lafayette Co, AR?