Local Agenda 21 (LA21) emerged 23 years ago as a voluntary policy innovation for local governments aiming at sustainability and has now completed its lifecycle. We aim at a second look at LA21 from the standpoint of the institutional and innovation diffusion theories and with Portugal as case study. Results show a three moment lifecycle for LA21, each with distinct diffusion patterns. The Dawn, stymied by lack of regional and national leadership, was likely fuelled by a learning mechanism. It lasted 10 years and involved a mere 1% of the potential adopters. The Zenith took place when other countries had already come full circle. During this phase27% of the local governments became active and both coercion and competition stand out as relevant engines. Twilight, most probably powered through coercion, competition and imitation mechanisms, took LA21 to a steady statewith an additional 19% of local governments enrolling. Since then LA21 has shown departures in several different directions, including oblivion. We speculate, based on preliminary data that,although most LA21 are no longer active, a durable setting was created that promotes further innovation and public participation.