1. Why American people celebrate Labor Day the first Monday of September?

http://www.history.com/minisite.do?content_type=Minisite_Generic&content_type_id=316&display_order=1&sub_display_order=1&mini_id=1060

http://www.dol.gov/opa/aboutdol/laborday.htm

http://www.apples4theteacher.com/holidays/labor-day/about.html

2. Why do people say not to wear white after Labor Day?

http://media.www.thehilltoponline.com/media/storage/paper590/news/2002/09/10/LifeStyle/Wearing.White.After.Labor.Day-270385.shtml?sourcedomain=www.thehilltoponline.com&MIIHost=media.collegepublisher.com

http://askville.amazon.com/people-wear-white-Labor-Day/AnswerViewer.do?requestId=8951725


3. What is the relation between the Knight of Labor and the Labor Day?

www.kinghtsoflabor.org

http://en.wikipedia.org/wiki/Knights_of_Labor