Mark -- Since Howard County was formed after the war from parts of four existing counties, it's difficult to give you a 100 percent accurate list; however, here are the companies I can say with complete confidence were organized in what is now Howard County:

Co. F, 4th Arkansas Regiment State Troops.
Co. B, 19th (Dawson's) Arkansas Regiment Infantry.
Co. C, 19th (Dawson's) Arkansas Regiment Infantry.
Co. I, 19th (Dawson's) Arkansas Regiment Infantry.

I'm pretty sure that part of Newton's Regiment Arkansas State Troops (Cavalry) was recruited in what is now Howard County, but that regiment's records are too fragmentary to say for sure.

Sorry I couldn't be of more help.