Pittsburgh (Pitts'burg), the second city of Pennsylvania, is built on a narrow strip of land where the Allegheny and Monongahela rivers meet to form the Ohio: it extends 7 or 8 miles up the rivers, and 2 or 3 down the Ohio. By rail it is 444 miles from New York, 354 from Philadelphia, and 468 from Chicago. Allegheny City (q.v.), north of the Allegheny River, is a distinct municipality. The business portion of Pittsburgh is on a plain, less than a mile in width, while the hills are covered with handsome residences. In this region, where the prevailing soft shales and sandstones have been worn away by the rivers to a depth of 500 or 600 feet, the horizontal layers of coal are exposed; the great Pittsburgh coal layer, 8 feet thick, like a broad black band extends around the city 300 feet above the river. The court-house, costing $2,500,000, is of Quincy granite, and is connected with the jail by a 'bridge of sighs.' The government building cost $1,500,000, and there are besides a city hall, the Exposition Building, a large R. C. cathedral, and Trinity Church (Episcopal). Pittsburgh is the seat of a Catholic college; its Carnegie free library was built, and the Carnegie Institute built and endowed, in 1890. The three rivers are crossed by fifteen bridges; and the different parts of the city are connected by several lines of electric cars.

Pittsburgh is now one of the most important industrial cities in the United States. The district, which practically extends over 25 miles up the Allegheny and Monongahela rivers and 10 miles down the Ohio (including the allied boroughs of Allegheny and McKeesport and about thirty smaller boroughs), is the great centre of the steel, iron, and glass industries of the United States. Its coalfields are very rich, and it is an extensive shipping-point for bituminous coal. Including the great Carnegie steel-works at Homestead, and the Westinghouse works, the district contains nearly 3500 manufactories, with an estimated capital of over $1,800,000,000, and employing over 240,000 people. Its manufactures include everything that can be made of iron, from a 58-ton gun to nails and tacks; steel in its various applications; all descriptions of glass and glassware; silver and nickel-plated ware; Japan and Britannia ware; pressed tin, brass, copper, bronzes; earthenware, crucibles, lire-pots, bricks; furniture, wagons and carriages; brushes, bellows, mechanical supplies of all kinds; natural-gas fittings, and tools for oil and gas wells. After 1883 natural gas was largely used for domestic and manufacturing purposes; but of late the supply is less abundant, and the manufactories have returned to the use of coal. Over $15,000,000 have been spent in dams and locks on the Allegheny, Monongahela, and Ohio, to give slack-water navigation, and an ultimate expenditure of $50,000,000 is contemplated. The traffic on these rivers is enormous, chiefly coal and iron manufactures. Much lumber-rafting is done on the Allegheny. The assessed value of Pittsburgh in 1903 was $375,163,000, and the revenue for general purposes was just over $7,094,200. In 1754 a few English traders built a stockade here, but were driven away by the French. The latter replaced the stockade by a fort, which, in honour of the governor of Canada, they called Duquesne. In 1758 it was taken by the English, who next year commenced a large and strong fortification, which, in honour of the elder Pitt, then prime-minister, they called Fort Pitt. The settlement became a borough in 1804, and in 1816 was incorporated as the city of Pittsburgh. Pop. (1810) 4768; (1840) 21,115; (1870) 86,076 (with Birmingham, included soon after, 121,799); (1880) 156,389; (1900)321,616.