The mechanical properties of a cell's environment can alter behavior such as migration and spreading, and control the differentiation path of stem cells. Here the authors describe a technique for fabricating substrates whose rigidity can be controlled locally without altering the contact area for cell spreading. The substrates consist of elastomeric pillar arrays in which the top surface is uniform but the pillar height is changed across a sharp step. Preliminary results demonstrate the effects on cell migration and morphology at the step boundary.