The core of this book consists of essays originally posted on the blog of the Cold War and Internal Security (CWIS) Collection, belonging to Academic Library Services, East Carolina University. The end result is a collection of 24 self-contained chapters, organized into five chronological/topical sections, covering various aspects of the efforts of the House Un-American Activities Committee (HUAC) and other 20th Century congressional committees investigating real or alleged subversion. These entries have been revised, updated, and merged as needed. There is also an introductory essay that explores the broader history of congressional countersubversive investigations. Each brief essay contains its own list of sources. The entries span a variety of topics from the birth of congressional countersubversive investigations in the First World War and aftermath of the Bolshevik Revolution, all the way up to Russian election influence efforts in 2016-2020, and congressional investigations of white nationalism. Topics covered in-between include the origins of the House Un-American Activities Committee, the tragic injustice that was the internment of Japanese-Americans in World War Two, various aspects of McCarthyism and the Red Scare, especially the role of congressional committees such as HUAC, the 1960 Martin/Mitchell affair, the Black Panthers, and aspects of the broader Cold War espionage and political/information struggle. This volume is intended to provide an overview and guide to further research for students, members of the public, and professional scholars.