Ironically, the chemical that would ultimately cause the explosion of the S.S. Grandcamp was not manufactured in Texas City. The fertilizer compound aboard the S.S. Grandcamp had originally been manufactured in War Department ordinance plants in Iowa and Nebraska. It was packed into 100-pound bags, mixed with rosin to prevent caking, and shipped by rail to Texas City. Warm temperatures along the way may have increased the reactivity of the substance; several longshoremen remembered the bags being warm to the touch upon their arrival in Texas City.
During World War II, ammonium nitrate was used to make TNT, but after the war it was often diluted and used as a fertilizer for crops. In its purest form, ammonium nitrate is not flammable, but it must be kept at cool temperatures. It becomes dangerous if combined with an explosive agent such as a blasting cap or volatile substances like sulfur, sugar, zinc, and copper.
At the time of the Texas City disaster, few federal or bureaucratic regulations regarding ammonium nitrate were enforced. Many modern safety practices were not yet in existence in the chemical industry, and little thought had been invested in planning how to manage a large-scale chemical disaster. In a detailed report following the disaster, a vice-president of the Texas City Railway Co. testified that he considered ammonium nitrate to be relatively safe compound — even comparing it to handling cement — and hadn't considered any precautions for transferring the cargo.1,4