The History of Black Friday in the USA from Wikipedia:
Black Friday is the Friday following Thanksgiving Day in the United States (the fourth Thursday of November). Since the early 2000s, it has been regarded as the beginning of the Christmas shopping season in the US, and most major retailers open very early and offer promotional sales. Black Friday is not a public holiday, but California and some other states observe "The Day After Thanksgiving" as a holiday for state government employees, sometimes in lieu of another federal holiday such as Columbus Day. Many non-retail employees and schools have both Thanksgiving and the day after off, followed by a weekend, thereby increasing the number of potential shoppers. It has routinely been the busiest shopping day of the year since 2005, although news reports, which at that time were inaccurate, have described it as the busiest shopping day of the year for a much longer period of time.
In 2013, approximately 141 million U.S. consumers shopped during Black Friday, spending a total of $57.4 billion, with online sales reaching $1.2 billion.
The day's name originated in Philadelphia, PA, where it originally was used to describe the heavy and disruptive pedestrian and vehicle traffic that would occur on the day after Thanksgiving. Use of the term started before 1961 and began to see broader use outside Philadelphia around 1975. Later an alternative explanation was made: that retailers traditionally operated at a financial loss ("in the red") from January through November, and "Black Friday" indicates the point at which retailers begin to turn a profit, or "in the black".