The widescreen format was first made popular by the 1953 release of The Robe. Filmed in Cinemascope and released by 20th Century Fox, The Robe was the studio's competition against the television, which was starting to surge in popularity. In order to get viewers back into the movie theatres, the Hollywood studios started to make their movies in widescreen and in other formats such as 3D, none of which could be replicated on the televisions of the day.
However, not all movies were made in widescreen. Movies that were made before The Robe were filmed in the Academy aspect ratio of 1.33:1 (more commonly known as 4:3), which televisions adapted for their displays. Many movies since then were filmed in the Academy aspect ratio. Even the 1999 release of Stanley Kubrick's Eyes Wide Shut was framed for a 1.33:1 release. Other popular movies that were filmed in the Academy aspect ratio include The Wizard of Oz, Casablanca, and Citizen Kane.
Because such movies were not filmed in a widescreen format, there should never be widescreen versions of such movies. This is a common misconception among many people.
Movies are not the only medium to be threatened by the inappropriate use of widescreen. For decades all television shows were recorded in the Academy aspect ratio. This has only recently changed with the popularity of 16:9 televisions. In fact, you will now have a difficult time finding 1.33:1 televisions in most electronics stores in the United States.
Unfortunately, a large number of people still expect their widescreen TVs to be "full". To accommodate this, some studios are improperly formatting Academy ratio movies and TV shows to a 16:9 aspect ratio by cutting off the top and bottom even though such removals were not a part of the intended framing. Such examples of improper widescreen formatting include the DVD releases of the first season of the original Kung Fu TV series (Warner Brothers) and A Christmas Carol (1951, DVD release by VCI Entertainment), both of which are available in 16:9 format.
Below is an example from The Wizard of Oz. The image on the left is the frame in its correct aspect ratio. The center image shows what could happen in a "false widescreen" presentation. The right image shows how the movie should be presented on a 16:9 television.
Improperly cropping a 1.33:1 frame to fit in a 16:9 screen results in the loss of the upper and lower portions of the frame and therefore violates the principles of "original aspect ratio". The proper way of displaying movies and TV shows that were filmed in Academy is to "pillarbox" the image to that there are black bars on the sides of the frame.
Contrary to what you might think of this site and its degree of widescreen advocacy, a widescreen release of a movie or TV show that was never in widescreen is as unacceptable as a pan-and-scan release of a widescreen movie. In either case the intended framing of the movie or TV show is being violated and should not be tolerated.