Star Wars had 3 versions in its original release, 70mm with 6 track dolby stereo, 35mm dolby stereo, and 35mm mono. Supposedly only 32 theaters were equipped to handle the 70mm 6 track version. 35mm mono is the format the vast majority of people saw it in back in 1977.
Here is some interesting trivia on the stereo myths regarding Star Wars:
"Another matter of interest (and controversy) is the presentation type audiences experienced in the opening weeks of release. Numerous books, trade publications, magazine and Internet articles, and fan recollections have over the years attributed "Star Wars" as having an exclusive opening in the "Dolby Stereo" process ("Dolby System" as it was then known), or having an exclusive "70mm Six-Track Dolby Stereo" opening with the 35mm versions appearing weeks later, or that the movie was the first ever to be released in Dolby Stereo. None were true! A few films were released in various forms of Dolby Stereo prior to "Star Wars" on a limited or test engagement basis such as "Tommy" (1975), "Nashville" (1975), "Lisztomania" (1975), "Logan's Run" (1976), and "A Star Is Born" (1976), though "Star Wars" was the first attempt at a wide release in the format. It appears that the distributor sought to book the film at the producers' urging in as many theatres as possible willing to install Dolby sound systems. The number of suitably-equipped venues, however, fell short of the total number of prints initially put into circulation. As for release prints in the deluxe (and expensive to produce) 70-millimeter format -- with its superior projection quality and exquisite six-track magnetic audio capability -- they were kept to a minimum. "
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