The Middle Colonies were often called the "breadbasket" of the colonies because they grew so many grains, like wheat and barley. Livestock like pigs or cattle was often raised and dairy farms produced milk, cheese, and other dairy products.
The Middle Colonies had coastal cities where ships came in and many colonists traded. There were many people living in the cities, many of them eating grains from farms. Supply ships often arrived.
There was lots of copper, coal, and iron around the coastal cities, leading many people to trade these ores or to work in the mines. There was also a steady supply of animal furs in that area.