The first Monday of September, America's workers' holiday, signed into law six days after federal troops crushed the Pullman strike.
Documented
The 1882 parade
The first Labor Day parade marched through New York on September 5, 1882, organized by the Central Labor Union. Credit is still fought over: carpenter Peter J. McGuire and machinist Matthew Maguire both proposed versions of the holiday, and both attended that parade.
Assessment: Documented: the parade and the rival claims are in the union record.
Stories
The Pullman penance
In June 1894, after the federal government broke the Pullman strike with troops and deaths, Congress rushed a national Labor Day bill to President Cleveland, who signed it days later. The speed was not coincidental: it was a peace offering to a furious workforce.
Assessment: Documented: the legislative timeline sits inside the strike's aftermath.
Interesting claims
Not May 1
Choosing September over the international May 1 distanced the holiday from Haymarket and socialism, a motive widely reported at the time. The result: the country whose workers inspired the world's labor day is nearly alone in not observing it.
Assessment: Interesting claims: a calendar decision as an act of political distancing.
Sources and further reading
US Department of Labor and historical record: the first Labor Day parade, New York, September 5, 1882, Central Labor Union
History.com, 'The Controversy Over Who Founded Labor Day': the Peter J. McGuire vs Matthew Maguire dispute
Congressional record, June 1894: the federal Labor Day bill signed by Grover Cleveland six days after the Pullman strike ended
Contemporary press on the choice of September over May 1 to avoid Haymarket associations
Worth asking
America celebrates labor in September specifically to not celebrate it with the rest of the world in May; what else is hidden in a date?