Mission 66, a boldly conceived and intensively planned ten-year program, aimed to avert a crisis. It would provide the developments urgently needed if the national parks, already suffering severely from overuse, were to continue to fulfill their statutory but contradictory obligations of preservation and public enjoyment. Public use of the parks was growing at an alarming rate and would exceed the planners' estimates for the decade ahead. In this situation museums were among the many factors that could help save the parks.

Good museums played a double role. They contributed to visitors' understanding and therefore enjoyment of a park. And visitors who understood and appreciated the significance of park features tended to treat them protectively.43 The nature of the problem, however, led Mission 66 planners to think in terms of a facility to serve a broader spectrum of visitor needs than previously associated with museums.

With the advent of PWA-funded administration/museum buildings in historical areas, most park museums shared space in multipurpose structures. The planners for Mission 66 built on this precedent. Visitors would find the new type of facility without difficulty thanks to more emphasis on strategically planned siting. It would recognize their needs as travelers and welcome them with restrooms and drinking fountains. It would provide helpful answers to their most pressing questions: where to eat and sleep, how to reach the park's prime features, how to plan their available time effectively. The building would therefore require a suitably spacious lobby with an efficiently staffed information desk as well as clear maps, schedules, and self-service orientation or information displays. It would have an auditorium or smaller room in which a relatively brief audiovisual presentation would either suggest what to see and do in the park or evoke an emotional anticipation toward important park themes. The museum exhibit room would offer a more cognitive introduction to the park story but also aim to send visitors quickly out into the park better prepared to understand and appreciate it. Those with more time and special interests would usually find here the museum study collection, the park library, and the offices or workrooms where they might consult other staff members.

While in earlier multiple-use situations the building was ordinarily referred to as the park museum, the planners wanted to call the new mix by a name that would make its service function crystal clear to the public. After some debate consensus favored "visitor center." The prompt retroactive application of the term to the pre-Mission 66 projects at Grand Canyon, Jamestown, Yorktown, and elsewhere demonstrated its general acceptance.

Most parks wanted one or more visitor centers as part of their Mission 66 development. By the time the program won administration and congressional approval in early 1956, the Museum Branch knew that it would have to plan and prepare approximately one hundred new museums within the next decade, an average of about ten per year. While welcoming the challenge, the branch feared that eagerness for modern visitor facilities might lead some parks to request unneeded museums. It therefore urged Mission 66 planners to propose museums only where necessary to preserve original objects important to a park's mission or essential to help visitors understand a park.