A plan of Pittsburgh from 1903 showing principal streets, railroads and stations, bridges, and landmarks. "Pittsburgh, the second largest city of Pennsylvania, and the leading iron, steel, and glass manufacturing center of the United States, lies at the confluence of the Allegheny and the Monongahela, which unite here to form the Ohio, 250 miles west by north of Philadelphia. The business quarter of the city is built on a nearly level triangular plain, between the two rivers, measuring about three quarters of a mile on each side back to the hills which rise to the east." - Kellogg, 1903.