In late 2011 to early 2013, the Greenville County (South Carolina) Enforcing Underage Drinking Laws (EUDL) Coalition led community efforts during a National Highway Traffic Safety Administration (NHTSA) demonstration grant. The Phoenix Center subcontracted with PIRE to assist as an evaluator and grant coordination consultant to work with enforcement partners, collect data, and report the process and outcomes of the project. The Coalition worked throughout Greenville County with a primary goal to deny alcohol to individuals under 21 years old utilizing a multi-pronged approach. In previous research, high visibility enforcement campaigns (HVE) are an evidence-based approach that has demonstrated effectiveness in the areas of increased seat belt usage and decreased alcohol-related crashes. The HVE approach combines multiple waves of strict enforcement with strong media messages occurring at each enforcement wave. Researchers have shown that HVE reduces the issues associated with underage drinking and adult provision of alcohol to youth. The strategic plan developed by the Greenville Coalition for the grant merged source investigation with HVE waves occurring throughout the project period. The primary evaluation conducted by the Coalition focused on using community-specific monthly times-series data measures to compare pre-HVE mean alcohol crash data to post-HVE mean alcohol crash data. Results indicated that crashes for < 21 year olds decreased 11.8% while the control group (21+ year olds) in alcohol crashes increased 19.4% during the project period. The program outcomes suggest the HVE/source investigation approach holds significant promise to reduce the harms of underage drinking in communities.