Decarceration is a national effort to shrink prison populations while preserving public safety. Since 2018, Washington advanced judicial, legislative, and administrative reforms that lowered imprisonment without sustained increases in recidivism or technical violations. Using monthly administrative data and interrupted time series analyses, this study estimates the effects of four milestones: 1) COVID-19 in March 2020, 2) State v. Blake in February 2021, 3) the temporary statute followed by the permanent Blake Fix in August 2023, and 4) the statewide rollout of iCoach in June 2023. Admissions fell sharply at COVID-19, the Blake ruling had limited direct effects, the Blake Fix was followed by modest upward trends in admissions, and iCoach coincided with immediate declines and a sustained drop in technical violations. Overall, decarceration was achieved when paired with credible community supervision and reentry capacity. By the end of the period, re-admissions, first admissions, and violations were about 75%, 90%, and 45% lower respectively, than projected levels had no policy changes occurred. COVID-19 produced large immediate drops across outcomes, followed by a temporary rise in re-admissions as systems adjusted. Overall, the Blake decision reduced felony drug enforcement, yet the changes that followed did not produce a measurable shift in returns to prison. The Washington decarceration experience was a process, rather than a single act, and resulted in a smaller prison population with no sustained rise in recidivism or technical violations.