At the turn of the 20th century, ironworkers in Omaha, many affiliated with the Knights of Labor, were helping build major structures like the downtown auditorium and post office, earning 20¢ an hour. Around this time, ironworkers from Chicago, including Billy McCain, moved to Omaha. McCain led efforts to obtain a charter from the Ironworkers International, and on June 24, 1901, Local 21 was officially established. Wages rose to 22.5¢ an hour following organization.

In 1942, Local 21 partnered with the federal Bureau of Apprenticeship and Training, ensuring high standards in the trade. Today, its four-year apprenticeship includes 816 hours of classroom instruction and 8,000 hours of fieldwork, with wages starting at 65% of journeyman pay and increasing every six months.

In 2006, Local 184 of Sioux City, Iowa merged with Local 21, expanding its reach and efficiency. Now serving Nebraska, Western Iowa, and South Dakota, Local 21 continues to provide skilled, union-trained ironworkers for the region’s future.