Houston’s quick growth between 1940 and 1960, when its population rose from twenty-first to seventh place among American cities, owed to the linking of three benefits: the ship channel, which gave the city access to the world; immense resources of oil, natural gas, sulphur, lime, salt, and water; and the fact that the product of one chemical plant is often the raw material of another. This combination created on the banks of the ship channel one of the world’s greatest concentrations of petrochemical industries—chemical plants dependent on the by-products of refining oil. The tempo increased in the early 1960s, when the Monsanto Chemical Company began building the world’s largest ethylene plant at a cost of fifty million dollars. Du Pont began building a hydrofluoric acid plant, and an important polypropylene plastic and film plant was being built. [Illustration: _The Houston Post Office, completed in 1962._] During the 1950s Houston was a leading example of the new urban America caused by the economic impetus of World War II and the increased post-war migration of rural people to cities. No period in the city’s history approaches the importance of World War II and the years after. Before the war Houston was an ambitious small city. A few years afterward, its former hopes lying in the shadows of sudden and preposterous growth, the city was altered in character, aspirations, and appearance. Houston’s formidable roles in the oil and gas industries, in the manufacturing of oil-field equipment, and in the nationwide distribution of gas are widely understood but seldom comprehended. The metropolitan area alone, which has seven oil refineries, produces nearly eighty thousand barrels of oil daily. Two major oil companies, the Humble Oil and Refining Company and the Continental Oil Company, and hundreds of smaller ones have their headquarters in Houston, most of whose downtown skyscrapers were built by or for oil, gas, and banking. The Tennessee Gas Transmission Company was organized in 1944; twelve years later its assets passed a billion dollars, a speed of growth that may never have been equaled in American business. Paul Kayser, president of the El Paso Natural Gas Company, was asked at a press conference in El Paso why his company, which owns El Paso’s tallest building and supplies West Texas gas to western states, has its headquarters in Houston. He answered that the only place in America to keep in touch with the oil business is Houston. [Illustration: _Freighters docked in the Port of Houston._] In 1960 most of the nation’s sulphur deposits, around 6 per cent of its petroleum reserves, and around 10 per cent of its refining capacity were in a nineteen-county area surrounding Houston. An estimated three-quarters of the nation’s petrochemicals production comes from the Texas Gulf Coast area. Shipbuilding, an integrated steel mill, and paper mills are other important aspects of the city’s economy.