Why do we have Labor Day?

This morning my wife asked me why we have Labor Day. I had no good answer. For those interested, here is an explanation:

Labor Day is a United States federal holiday that takes place on the first Monday of September. In 2006, Labor Day occurred on September 4.

The origins of the American Labor Day can be traced back to the Knights of Labor in the United States and a parade organized by them on September 5, 1882 in New York City. They were inspired by an annual labor parade held in Toronto, Canada. In 1884 another parade was held, and the Knights passed resolutions to make this an annual event. Many other labor organizations, notably the affiliates of the International Workingmen's Association, favored a May 1 holiday. With the event of Chicago's Haymarket riots in early May of 1886, president Grover Cleveland believed that a May 1 holiday could become an opportunity to commemorate the riots. Thus, fearing that it might strengthen the socialist movement, he quickly moved in 1887 to support the position of the Knights of Labor and their date for Labor Day.

Labor Day has been celebrated on the first Monday in September in the United States since the 1880s. The September date has remained unchanged, even though the government was encouraged to adopt May 1 as Labor Day, the date celebrated by the majority of the world. Moving the holiday, in addition to breaking with tradition, could have been viewed as aligning the U.S. labor movements with internationalist sympathies.

Labor Day is generally regarded simply as a day of rest and, unlike May Day, political demonstrations are rare. Forms of celebration include picnics, barbecues, fireworks displays, water activities, and public art events. Families with school-age children take it as the last chance to travel before the end of summer. Some teenagers and young adults view it as the last weekend for parties before returning to school. However, of late, schools have begun well before Labor Day, up to the 15th of August in many urban districts, including Nashville and Atlanta.
One of the largest modern traditions of Labor Day in the United States is the annual telethon of the Muscular Dystrophy Association, hosted by Jerry Lewis to fund research and patient support programs for the various diseases grouped as muscular dystrophy. The telethon raises tens of millions of dollars each year.
According to Howard Zinn in his research in A People's History of the United States, the original parade in 1882 organized by the Knights of Labor had a loose affiliation with the Ku Klux Klan, a main reason why the more progressive supporters of a labor parade prefered the May Day march.

From Wikipedia.org