This report represents Volume I of the All-domain Anomaly Resolution Office’s (AARO) Historical Record Report (HR2) which reviews the record of the United States Government (USG) pertaining to unidentified anomalous phenomena (UAP). In completing this report, AARO reviewed all official USG investigatory efforts since 1945, researched classified and unclassified archives, conducted approximately 30 interviews, and partnered with Intelligence Community (IC) and Department of Defense (DoD) officials responsible for controlled and special access program oversight, respectively. AARO will publish Volume II in accordance with the date established in Section 6802 of the National Defense Authorization Act for Fiscal Year 2023 (FY23); Volume II will provide analysis of information acquired by AARO after the date of the publication of Volume I.