Festival Express was a combination rock concert and train ride across Canada that happened in 1970 and featured the Grateful Dead, The Band, Janis Joplin and many others. The footage was released as a movie in 2003. A brother discovered the full video on a Russian server. This link may not last, so I'd suggest you watch it and if you'd like, download it ASAP. This is a classic.
Warning: If you don't have a fast broadband connection, let it load overnight.