Downtown Pittsburgh is a 300-acre triangle of land where the Allegheny and Monongahela Rivers converge to form the mighty Ohio River. Between the rivers is a tiny spit of flat-bottom land once known as the gateway to the West, the portal to a vast, remote, unexplored wilderness. Ownership of this strategic wedge of land was fiercely contested for hundreds of years. The powerful Iroquois Nation first invaded the area in the 1600s during the Beaver Wars. When the French planted their flag in 1749, they collided with the British Empire for control of the forks of the Ohio River and all of North America. One hundred years later, this swath of frontier wilderness became the workplace of the world, the heart of the great Industrial Revolution. Immigrants arrived from around Europe to work in the glass, iron, and steel mills. Industrial giants such as Carnegie, Frick, Mellon, and Heinz forged their fortunes here. Downtown Pittsburgh is the story of the great transformation of this city and its contributions to the world.