My understanding of what little records that I have seen is that the pre war 24th Arkansas Militia Regiment consisted of two companies of Infantry ( Company "H" of the 2nd AR. Inf., Co. "B" 15th AR. Inf.,) a company of Cavalry (Co. "D" 2nd Arkansas Batt.) and a company of Artillery (Pine Bluff Artillery) the Pine bluff artillerys gun was at the center of a contriversy when it was siezed at Cinncinnati, Ohio.
There was possibly a third company of militia Infantry of which I am not quite sure of. These are the men who became Co. "D" "Clan McGregor" of Fagan's 1st AR. Inf. I haven't been able to determine where these men came from. Since Donaldson McGregor the Captain of that comapny was the Colonel of the 24th Ark Militia I suspect that this company was a composite of volunteers made up of men from the other two Infantry companies of the 24th AR. Militia.
In any case these 3 companies were the first rush of volunteers in May 1861 to form companies, They were quickly followed by July by 4 more companies in the 9th AR. Inf., and in September by an 8th company Co. "B" 2nd Ark. Inf., Battalion.