The paper describes the application of a general purpose optimization code, PARS to the design of the sides of a 100 ton high side gondola car. PARS (Program for Analysis and Resizing of Structures), a companion code to the SPAR finite element package, is used for optimizing structures modeled by finite elements. The optimization algorithm uses an extended interior penalty function and Newton's method for unconstrained minimization.The sides of the gondola car are modeled by beam and plate finite elements. Manufacturing requirements are accounted for by design variable linking and the sides are designed subject to stress and displacement constraints. The design is obtained according to the specifications for design, fabrication and construction of freight cars recommended by the Association of American Railroads.