quote [ This site was created by The Black Vault to house 129,491 pages, comprising of more than 10,000 cases of the Project Blue Book, Project Sign and Project Grudge files declassified. Project Blue Book (along with Sign and Grudge) was the name that was given to the official investigation by the United States military to determine what the Unidentified Flying Object (UFO) phenomena was. It lasted from 1947 - 1969. Below you will find the case files compiled for research, and available free to download. ]