The evidence for and our understanding of community-level strategies such as policies, system, and environmental changes that support healthy eating and active living is growing. However, researchers and evaluation scientists alike are still not confident in what to recommend for preventing or sustaining declines in the prevalence of obesity. The Systematic Screening and Assessment (SSA) methodology was adapted as a retrospective process to confirm obesity declines and to better understand what and how policies and programs or interventions may contribute as drivers. The Childhood Obesity Declines (COBD) project's adaptation of the SSA methodology consisted of the following components: (1) establishing and convening an external expert advisory panel; (2) identification and selection of sites reporting obesity declines; (3) confirmation and review of what strategies occurred and contextual factors were present during the period of the obesity decline; and (4) reporting the findings to sites and the field. The primary result of the COBD project is an in-depth examination of the question, "What happened and how did it happen in communities where the prevalence of obesity declined?" The primary aim of this article is to describe the project's methodology and present its limitations and strengths. Exploration of the natural experiments such that occurred in Anchorage, Granville County, New York City, and Philadelphia is the beginning of our understanding of the drivers and contextual factors that may affect childhood obesity. This retrospective examination allows us to: (1) describe targeted interventions; (2) examine the timeline and summarize intervention implementation; (3) document national, state, local, and institutional policies; and (4) examine the influence of the reach and potential multisector layering of interventions.