Did you ever succeed in establishing when they were formed? There is a Wikipedia Article on the Arkansas Militia in the Civil War that I have contributed to which lays out the relationship between the militia and the volunteer companies that were formed. The volunteer companies were actually authorized by the Arkansas Militia Law and Governor Conway put out a call in 1860 for their formation. In 1861 the legislature passed a law appropriating money to help arm the volunteer companies authorized by the militia act. As soon as the state succeeded, the State Military Board issued a call for troops and new volunteer companies started forming. It was at this time that the volunteer companies loose their connections to the prewar militia. The Confederate government eventually authorized several individual to raise regiments in the state. Some of these included prewar volunteer companies (militia) companies and some were new companies rised directly for confederate service. I am trying to run down each one of the named volunteer companies and try and determine it's connection to the pre-war militia. The militia law required the election of officers to be certified by the local militia regimental commander, so that is the test that I have been using in the Wikipedia article. The Yell Rifles and the Phillips County Guards bear all the hallmarks of a volunteer militia company. They clearly existed before the seizure of the Arsenal in February 1861, which was three months before secession, but I cannot find records of their actual formation.