This document provides an overview of elite theory, beginning with its origins in the late 19th/early 20th century Italian School led by Gaetano Mosca, Vilfredo Pareto, and Roberto Michels. It examines how their work established the idea that societies are divided between a small, organized ruling minority and a disorganized majority. It then discusses how elite theory was applied in the US, notably by C. Wright Mills who argued America had an integrated power elite across political, economic, and military institutions. The document also summarizes debates between pluralist and elitist approaches to power structures.