Answer:
Philadelphia in the state of Pennsylvania, USA.
Step-by-step explanation:
The term "Black Friday" more generally meant the huge number of shoppers on the day after Thanksgiving which falls on the last Friday of November. This phenomena of shoppers thronging the shops in huge numbers led to the terminology of "Black Friday" as it also refers to the huge traffic snarls and pedestrians who are out shopping. This day also is regarded as the first day of 'Christmas shopping', where people start their shopping for the upcoming Christmas celebration.
The Pennsylvanian state of Philadelphia is believed to be the place of origin for this "Black Friday" term when in around 1961 when the people noticed a huge traffic block due to the huge number of shoppers/ pedestrians on that day right after the Thanksgiving festival. This then came to be labelled as a regular phenomenon, and with the huge advantage f attracting customers, shops began giving huge offers and various discounts for this particular day, further increasing the significance of the day.