The adoption of the Northwest Forest Plan in the early 1990s brought about fundamental shifts in forest management practices on federal lands in western Oregon and Washington. Commodity-driven clearcut regeneration harvests gave way to thinnings of young stands intended to accelerate the development of late-successional forest habitats and to conserve important aquatic and riparian ecosystems. Density Management in the 21st Century: West Side Story presents abstracts and peer reviewed papers from a 2011 regional conference highlighting more than 20 years of research related to the new practices of forest thinning and associated aquatic and riparian conservation measures. Collectively, the contributions summarize many important forest dynamics and ecosystem responses to partial overstory harvests. Targeting resource management practitioners, decision-makers and researchers, the collected works provide a reference to the current and future roles and issues of density management as a tool for forest ecosystem management. The various research synopses will be directly applicable to project-level planning and environmental analyses, as well as providing context for large-scale planning and policy discussions.