Peanut butter more or less as we know it today was popularized at the 1893 World Fair. In the early 1900s, peanut butter made frequent appearances in tea rooms across the nation where it was billed as a dish for rich people. Back then, it was paired with items, such as cucumbers, cheese, celery, and crackers. At that point, peanut butter was still considered a “high end” food and peanut butter and jelly sandwiches were not a commonly eaten food item.
Peanut butter spread to the masses during the 1920s and 1930s, shortly after pre-sliced bread came into existence. At that time commercial brands Skippy and Peter Pan began.
With the Great Depression, peanut butter on bread became a staple in many American households, because it provided a hearty, filling meal with a cheaper-than-meat substitute for protein.
During WWII the peanut butter and jelly sandwich became a popular meal among United States soldiers. When soldiers arrived home from the war, peanut butter and jelly sales skyrocketed.
The PB&J is a bigger hit in the United States than in most other countries.
The average American will eat around 1,500 peanut butter and jelly sandwiches by the time they turn 18.
Incidentally, peanuts are not nuts, they are legumes (a type of plant with seeds that grow inside pods like peas or beans). Nuts are grown on trees, peanuts grow underground. March is National Peanut Month.