This report describes a testing program examining the effects of different stages of tank car fabrication on the mechanical properties of TC-128B steel. This work focused on two procedures: cold-working associated with rolling a flat plate of steel into the cylindrical tank shell and post-weld heat treatment (PWHT). The Volpe National Transportation Systems Center developed a plan and executed a contract for tensile tests on TC-128B steel samples. TC-128B was provided in four different conditions by two different tank car builders: an “as-received” flat plate, a flat plate put through PWHT, a cold-worked shell, and a cold-worked shell put through PWHT. By characterizing the material properties at different stages of fabrication, the effect of each manufacturing process on the material’s behavior could be isolated. Cold-working did not have a consistent effect on strength or ductility, while PWHT increased ductility but reduced ultimate tensile strength.