had a center channel, it was the first of 76 features that had what was called "Three Channel Stereo":http://www.imdb.com/search/title?at=0&sort=year,asc&sound_mixes=3_channel_stereo&start=51
Before 1940 there was only Mono sound in regular theaters. IIRC one of the few places one could hear Fantasia
in multi channel sound was a dedicated theater in the original Disneyland.
In 1953, according to the IMDB list above, another 13 features were released in "Three Channel Stereo". The format is still used. So I believe that you could correctly state that the original multi-channel sound had a center speaker.
As to what you actually hear in the theater, that is a matter of the playback system. Most theaters had some combination of 'horn" tweeters and bass woofers in what was called a "ported" enclosure. The port increased volume by putting the sound from the rear of the woofer "in phase" with the front of the same speaker or speakers. The "horns" were highly efficient low distortion speakers in the midrange frequencies, making the dialogue very clear. There was not much sound above 10,000Hz in the theater, not only did the horns "roll off' the high frequencies, but they were located behind the fabric screens which also tended to muffle high frequencies.
Before Dolby noise reduction, there was a lot of noise and the high frequencies in soundtracks were often limited to improve clarity - resulting in a situation where every actor's voice on screen was deeper than in person.
The most popular mono sound speaker was the famous Altec-Lansing "Voice of the Theater":
...most often located in the center of the screen, and driven with a 15w vacuum tube amplifier. When multi-channel sound came along, good theaters added two more identical speakers, also behind the screen. But the cheap way to add the additional pair of speakers was to mount box speakers on the wall beside the screen. Large theaters often had multiple box speakers along the walls. This tended to muddy dialog because multiple speakers interacted and interfered with one another.
I would speculate that the concept of "stereo" as two channels came from music reproduction from vinyl discs and FM radio.