Jay Gould and Jim Fisk, two investors who caused a market crash by driving up gold prices in 1869, coined the term "Black Friday". This caused the stock market to drop 20%, foreign trade to stop, and corn and wheat prices to plummet.
In Philadelphia during the late 1950s and early 1960s, the term was resurrected and applied to the day between Thanksgiving and the Army-Navy game. Law enforcement would need to put in extra hours to moderate traffic during the event because it would draw large crowds of tourists and shoppers.
It wasn't until the late 1980s that the term became synonymous with shopping. It was retailers who renamed Black Friday after accountants used different colored ink to denote a company's profitability - red for negative earnings, black for positive earnings. It was on Black Friday that stores finally turned a profit.
It's no surprise that the name stuck, and since then Black Friday has evolved into a yearly shopping event that's led to the creation of more shopping holiday days, such as Small Business Saturday and Cyber Monday.