Reel-To-Reel is a magnetic tape format introduced in the US in 1949, the format saw the release of music from popular artists in the mid 1950's and found it's peak of popularity in the mid 1960's.  Beloved by hardcore audiophiles for it's superior sound quality, the format eventually declined and became obsolete by the 1970's.  As cheaper formats such as 8-Track and Cassette Tape were more widely embraced by consumers due to extremely lower costs.  To this day the format is still highly regarded by hardcore audiophiles and music history enthusiasts.