24/7 Wall St.

Labor Day. A celebration of America’s workers. It is 100 years old, at least in some states. There is a dispute about whose idea it was. As a stronghold of America’s workers, though much less than in the past, Labor Day has a special place in the heart of America’s labor unions.

Springfield, Illinois, is the U.S. city with the most unionized workers, according to a study by 24/7 Wall St. titled “14 Cities With the Strongest Unions.” The selection process was base on, among other things, this:

According to the labor department, workers with a high school diploma but not a college degree are among the most likely beneficiaries of union memberships. This particular group tends to be relatively large in the 14 cities on this list, where high school attainment rates tend to be above average but college attainment rates tend to be lower than in most U.S. cities.

Springfield did well in most of these measures:

> Pct. of workers in unions: 37.1%
> Union workers: 50,757
> Unemployment rate: 4.8%

No U.S. city has a higher share of workers who belong to a union than Springfield. The high union membership rate of 37.1% is partially due to the area’s high share of public sector workers — public sector workers are far more likely than private sector workers to be union members. The public sector employs 23.6% of the area’s workforce, one of the highest such percentages among U.S. metro areas and considerably higher than the comparable national share of 15.4%.

There are also a number of large unions based in the region. IBEW Local 193, a branch of the International Brotherhood of Electrical Workers, is based in Springfield. The Springfield Education Association, which consists of approximately 1,200 workers, as well as Teamsters, a union of freight, warehouse, and construction workers, also have a significant presence in the area.

Check out all 14 cities with the strongest unions.