Since its origin 23 years ago as a pilot test conducted in four U.S. counties, the U.S. Census Bureau's American Community Survey (ACS) has been the focus of continuous research, development, and refinement. The survey cleared critical milestones 14 years ago when it began full-scale operations, including comprehensive nationwide coverage, and 5 years later when the ACS replaced a long-form sample questionnaire in the 2010 census as a source of detailed demographic and socioeconomic information. Throughout that existence and continuing today, ACS research and testing has worked to improve the survey's conduct in the face of challenges ranging from detailed and procedural to the broad and existential. This publication summarizes the presentations and discussion at the September 26-27, 2018, Workshop on Improving the American Community Survey (ACS), sponsored by the U.S. Census Bureau. Workshop participants explored uses of administrative records and third-party data to improve ACS operations and potential for boosting respondent participation through improved communication.Table of ContentsFront Matter1 Introduction2 Administrative Records, Third-Party Data, and the American Community Survey3 Increasing American Community Survey Participation Through Improved Respondent CommunicationReferencesAppendixesAppendix A: Workshop Agenda and Participant ListAppendix B: Biographical Sketches of Planning Committee Members and PresentersCommittee on National Statistics