In teaching Arkansas History, the authors of the textbooks have always stated there were 8000+ white troops and about 5500 black for a total Union count of about 13,500+.

Counting the CS forces is a little more difficult due to those men who served in various units and might be counted twice and those who have no records available etc. But the general concensus is anywhere from 60,000 up to 72,000. It would take very detailed research to come up with close to exact figures.