A procedure is developed for designing low-cost or low-weight cantilever reinforced concrete retaining walls, with base shear keys, using big bang-big crunch (BB-BC) optimization. The objective of the optimization is to minimize the total cost or total weight per unit length of the retaining structure subjected to constraints on the basis of stability, bending moment, and shear force capacities and the requirements of the American Concrete Institute (ACI 318-05). An iterative population-based heuristic search method, BB-BC optimization has a numerically simple algorithm with relatively few control parameters as compared with other evolutionary methods. Low-cost and low-weight designs for two retaining walls are presented. In addition, results are presented on the effects of surcharge load, backfill slope, and internal friction angle of the retained soil on the values of low-cost and low-weight designs with and without a base shear key. DOI: 10.1061/(ASCE)ST.1943-541X.0000461. (C) 2012 American Society of Civil Engineers.