Say it with me: fair use!

All archival footage is being used as outlined in US Copyright law under 17 USC § 107 - Limitations on exclusive rights: Fair use. "Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright."