The Day After was the idea of ABC Motion Picture Division president Brandon Stoddard, who, after watching The China Syndrome, was so impressed that he envisioned creating a film exploring the effects of nuclear war on the United States. Stoddard asked his executive vice president of television movies and miniseries Stu Samuels to develop a script. Samuels created the title The Day After to emphasize that the story was not about a nuclear war itself, but the aftermath. Samuels suggested several writers and eventually Stoddard commissioned veteran television writer Edward Hume to write the script in 1981. The American Broadcasting Company, which financed the production, was concerned about the graphic nature of the film and how to appropriately portray the subject on a family-oriented television channel. Hume undertook a massive amount of research on nuclear war and went through several drafts until finally ABC deemed the plot and characters acceptable.
Originally, the film was based more around and in Kansas City, Missouri. Kansas City was not bombed in the original script, although Whiteman Air Force Base was, making Kansas City suffer shock waves and the horde of survivors staggering into town. There was no Lawrence, Kansas in the story, although there was a small Kansas town called "Hampton". While Hume was writing the script, he and producer Robert Papazian, who had great experience in on-location shooting, took several trips to Kansas City to scout locations and met with officials from the Kansas film commission and from the Kansas tourist offices to search for a suitable location for "Hampton." It came down to a choice of either Warrensburg, Missouri and Lawrence, Kansas, both college towns — Warrensburg was home of Central Missouri State University and was near Whiteman Air Force Base and Lawrence was home of the University of Kansas and was near Kansas City. Hume and Papazian ended up selecting Lawrence, due to the access to a number of good locations: a university, a hospital, football and basketball venues, farms, and a beautiful countryside. Lawrence was also agreed upon as being the "geographic center" of the United States. The Lawrence people were urging ABC to change the name "Hampton" to "Lawrence" in the script.
Back in Los Angeles, the idea of making a TV movie showing the true effects of nuclear war on average American citizens was still stirring up controversy. ABC, Hume and Papazian realized that for the scene depicting the nuclear blast, they would have to use state-of-the-art special effects and they took the first step by hiring some of the best special effects people in the business to draw up some storyboards for the complicated blast scene. Then, ABC hired Robert Butler to direct the project. For several months, this group worked on drawing up storyboards and revising the script again and again; then, in the spring of 1982, Butler was forced to leave The Day After because of other contractual commitments. ABC then offered the project to two other directors, who both turned it down. Finally, in May, ABC hired feature film director Nicholas Meyer, who had just completed the blockbuster Star Trek II: The Wrath of Khan. Meyer was apprehensive at first and doubted ABC would get away with making a television film on nuclear war without the censors diminishing its effect. However, after reading the script, Meyer agreed to direct The Day After.
However, Meyer wanted to make sure he would film the script he was offered. He didn't want the censors to chop up the film, nor did he want the film to be a regular Hollywood disaster movie from the start. Meyer figured the more The Day After resembled such a film, the less effective it would be. Meyer just wanted to dump the facts on nuclear war in people's laps. So first of all he made it clear to ABC that no TV or film stars should be in The Day After. ABC agreed, although they wanted to have one star to help attract European audiences to the film when it would be shown theatrically there. Later, while flying to visit his parents in New York City, Meyer happened to be on the same plane with Jason Robards and asked the star to join the cast.
Meyer plunged into several months of nuclear research, which made him quite pessimistic about the future. Every day, Meyer would come home feeling ill. He soon realized that what he was learning was making him sick. Meyer and Papazian also made trips to the ABC censors, and to the United States Department of Defense during this time. There were conflicts with both. Meyer had many heated arguments over elements in the script, both little and big, that the network censors wanted cut out of the film. The Department of Defense said they would cooperate with ABC if the script made clear that the Soviet Union launched their missiles first—something Meyer and Papazian took pains not to do.
In any case, Meyer, Papazian, Hume, and several casting directors spent most of July, 1982 taking numerous trips to Kansas City. In between casting in Los Angeles, where they stuck mostly to unknowns, they would fly to the Kansas City area to interview local actors and scenery. They were hoping to find some real Midwesterners for smaller roles. Hollywood casting directors strolled through shopping malls in Kansas City, looking for local people to fill small and supporting roles, while the daily newspaper in Lawrence ran an advertisement calling for local residents of all ages to sign up for jobs as a large number of extras in the film and a professor of theater and film at the University of Kansas was hired to head up the local casting of the movie. Out of the eighty or so speaking parts, only fifteen were cast in Los Angeles. The remaining roles were filled in Kansas City and Lawrence.
While in Kansas City, Meyer and Papazian toured the Federal Emergency Management Agency offices in Kansas City. When asked what their plans for surviving nuclear war were, a FEMA official replied that they were experimenting with putting evacuation instructions in telephone books in New England. "In about six years, everyone should have them." This meeting led Meyer to later refer to FEMA as "a complete joke." It was during this time that the decision was made to change "Hampton" in the script to "Lawrence." Meyer and Hume figured since Lawrence was a real town, that it would be more believable and besides, Lawrence was a perfect choice to play a representative of Middle America. The town boasted a "socio-cultural mix," sat near the exact geographic center of the continental U.S., and Hume and Meyer's research told them that Lawrence was a prime missile target, because 150 Minuteman missile silos stood nearby. Lawrence had some great locations, and the people there were more supportive of the project. Suddenly, less emphasis was put on Kansas City, the decision was made to have the city completely annihilated in the script, and Lawrence was made the primary location in the film.