This book is an overview of the petrochemical industry from the perspective of the author’s experience with Standard Oil, Scientific Design Co and Chemical Systems, Inc. The petrochemical industry is unique in its unusually rapid growth from its birth in the 1920s to maturity in the late 1970s. Between 1940 and 1960 it became one of the largest industry sectors, providing an astounding variety of chemical products used for the manufacture of plastics, fibers, synthetic rubber and many other products. An abundance of inexpensive gaseous and liquid petroleum feedstocks, suitable advanced technology, a large market and an incentive for rapid development occasioned by World War II and the consumer-oriented boom that followed have resulted in the development of this dynamic industry. This is a great achievement which deserves to be remembered at a time when the chemical industry is under a cloud due to a history of neglecting the environment and being insufficiently sensitive to health hazards.