Labor Day, holiday celebrated in the United States and Canada on the first Monday in September to honor the laborer.In most other countries–and among the leftists in the United States and Canada–May Day (May 1) is celebrated instead.

Why is Labor Day celebrated on September 1st in the US?

http://usa.usembassy.de/holidays-labor.htm
http://wilstar.com/holydays/laborday.htm

Main characteristics of this day (at least 4)

http://dol.gov/opa/aboutdo/laborday.htm
http://labor-day-weekend.com/labor-day-history.htm
http://wilstar.com/holydays/laborday.htm

When did this celebration start?
http://usinfo.pl/aboutusa/holidays/labor.htm