Why is the Day After Thanksgiving Called ‘Black Friday?’

The day after Thanksgiving is one of the biggest shopping days of the year with specials and sales at almost every retail and online store in the United States. It was first referred to as Black Friday because of the bedlam caused by bargain-hungry shoppers. The first recorded use is said to have been in an ad which referred to the term as used by Philadelphia police to describe those unruly crowds. It's also been said to describe the day on which retailers bottom line goes from the red to black due to the volume of sales. But with all the stores opening on Thanksgiving night, the real question is, will it evolve into Black Thursday?

[Via TodayIFoundOut.com and About.com]