Fifteen years ago, wig shops dominated East Fourth Street; the wigs in the windows were color-coded to correspond to the drugs for sale inside. In 2000, local developer MRN Ltd. used historic tax credits and abatements to begin to buy out 250 owners and create 224 apartments, for which there’s now a 400-person waiting list. More than a dozen restaurants, a House of Blues, and a bowling alley keep the lantern-strewn strip buzzing. Downtown needs retail and more residents, but East Fourth Street helped jump-start the revitalization.