when I was an attorney (until 1965 when I left to get my doctorate and hed for scthen to Syracuse to teach). My reply is based on stories told me by others since there were no casinos when I arrived in 1958. (Our Elks Club -- and I suspect others--had gambling items that would come out once a month.) During WW II there was an air force base and gambling was prolific with a number of unlicensed clubs. while I don't recognize any of the match names I assume they accurately tell the story of the 40's in Sioux Falls. Gambling was prolific in Dakota before being legalized in the 70's. One Elks Club lost its slots when an unlucky gamble lost his paycheck and his wife brought in the sheriff after the club refused to return his losses. I had a couple of chips from illegal Dakota clubs as well as many from the old Deadwood Clubs.
I don't know now who you could contact buy the police or the county Sheriff's might have records; also the Argus Leader archives could be searched for stories.