Answer:
Pittsburgh was the leading steel-producing area in the region due to its proximity to Appalachian iron ore and coal.
Step-by-step explanation:
Pittsburgh otherwise known as "The steel city" was once the major producer of iron and steel in America due to the large deposit of iron ore and coal at Appalachia.
Examining the period of industrial revolution in North America can be attributed to the massive steel production in Pittsburgh, which enhanced, building of rail and ships for the purpose of transportation, which in turns employed massive workers or labours in the area.
It is in this period, the well known millionaires acquired their massive wealth, such as Andrew Carnegie, Charles Schwab, Henry Phipps, Ben Franklin Jones and others.
This period also increased the massive exploration of coal, as it serves as source of energy for the industrial production of iron and steel.