A Day Called 'X' was a dramatized CBS documentary showing a civil defence exercise in Portland, Oregon in which the entire city is evacuated in anticipation of a nuclear air raid, after Soviet bombers had been detected by radar stations to the north. It was filmed in September 1957 and aired December 8 of that year. It was presented by Glenn Ford.
Its local rebroadcast in 2004 and appearance in the on-line Prelinger Archives attracted interest among local history buffs due to its extensive outside shots of the city, and the use of non-actor participants (local officials and broadcasters).
On September 27, 1955, Portland actually conducted an exercise evacuation of downtown called "Operation Greenlight," and the film is often misattributed to that year.