Cities in the middle colonies were mainly supported by the industry of **trade**. Trade played a vital role in the economic development of cities like Philadelphia and New York in the middle colonies. These cities were important hubs for exchanging goods and services, both within the colonies and with other regions. Trade allowed for the growth of businesses, the influx of goods from Europe and other colonies, and the establishment of markets where people could buy and sell various products. This industry helped to fuel the prosperity and development of the cities in the middle colonies.
