The Gold Line Foothill Extension represents an unprecedented light rail expansion into the San Gabriel Valley from downtown Los Angeles. In examining its potential for success, transit-oriented development (TOD) appears to be an integral factor and a major opportunity to redraw growth patterns along the corridor. TOD opportunities and challenges are investigated throughout the Foothill Extension, and three towns in particular, Claremont, Monrovia, and Irwindale, are examined on the basis of their varying levels of TOD planning. The corridor features many infill sites with potential for high density development near new Gold Line stations, but implementation of some TOD sites should be delayed until improvements in the economy can create appropriate short-term demand for office and retail space.