Black Friday as a term has been used in multiple contexts, going back to the nineteenth century, where it was associated with a financial crisis in 1869 in the United States. The earliest known reference to "Black Friday" to refer to the day after Thanksgiving was made in a 1966 publication on the day's significance in Philadelphia:
JANUARY 1966 -- "Black Friday" is the name which the Philadelphia Police Department has given to the Friday following Thanksgiving Day. It is not a term of endearment to them. "Black Friday" officially opens the Christmas shopping season in center city, and it usually brings massive traffic jams and over-crowded sidewalks as the downtown stores are mobbed from opening to closing.
The term Black Friday began to get wider exposure around 1975, as shown by two newspaper articles from November 29, 1975, both datelined Philadelphia. The first reference is in an article entitled "Army vs. Navy: A Dimming Splendor," in The New York Times:
Philadelphia police and bus drivers call it "Black Friday" - that day each year between Thanksgiving Day and the Army–Navy Game. It is the busiest shopping and traffic day of the year in the Bicentennial City as the Christmas list is checked off and the Eastern college football season nears conclusion.
Store aisles were jammed. Escalators were nonstop people. It was the first day of the Christmas shopping season and despite the economy, folks here went on a buying spree. ... "That's why the bus drivers and cab drivers call today 'Black Friday,'" a sales manager at Gimbels said as she watched a traffic cop trying to control a crowd of jaywalkers. "They think in terms of headaches it gives them."
The term's spread was gradual, however, and in 1985 the Philadelphia Inquirer reported that retailers in Cincinnati and Los Angeles were still unaware of the term.