This paper describes a method to analyze the history of hypermedia collections. We gathered information about documents using the Internet Archive’s Wayback Machine. Analysis focused on two key aspects: centroid migration and content migration. The objective is to understand how collections change over time. We developed and applied a tool called HHAT, or Hypertext History Analysis Tool, that visualizes centroids and content migration over time. Categories and Subject Descriptors H.5.4 [Information Interfaces and Presentation]: Hypertext/Hypermedia; H.3.7 [Digital Libraries]: Collection General Terms Measurement, Design. Keywords Hypertext/hypermedia, digital libraries, digital archives, centroids, content migration, Web evolution, Web characterization, Web pages.