Here are some places to learn more about the history of labor and labor unions in America:
For more on the Haymarket Square Riots in Chicago, the Chicago Historical Society maintains a website.
More on information on the Pullman Strike, which led to the passage of the Labor Day law, can also be found at the Public Broadcasting Service site on George Pullman.
You can read also read more about labor in American History in my book Don’t Know Much About® History
And you can follow my blogs about history and the headlines at www.dontknowmuch.com
Here's a TED-Ed Best Flip about Labor Day.