I found a small ad in the Rock & Gem August 2014 for the September shows, which might concern the same show, but according to this ad there might be a mix-up of locations between "Sioux City, Iowa" and "South Sioux City, Nebraska"
27-28—SOUTH SIOUX CITY, NEBRASKA: Retail show; Siouxland Gem & Mineral Society; S. Sioux City Senior Citizens Center; 1501 W. 29th St.; Sat. 9-4, Sun. 10-4; free admission; exhibits, four dealers, gems, agates, rough and polished specimens, beads, geodes, minerals, faceted jew- elry, fossils, door prizes, spin the wheel, silent auction, dis- plays, artifacts; contact Bob Powell, 406 Brandon, Kingsley, IA 51028, (712) 378 2775; e-mail: bobphyl.powell@gmail.com
Source:
http://www.rockngem.com/ftp/R&G_Aug14/files/assets/basic-html/page42.html