With the creation of the 25-mile-long Zion-Mount Carmel Highway, travelers could tour the Utah national parks in a loop. The now famous Zion-Mount Carmel Tunnel was part of this highway project.

Tour buses also became more popular at that time, as did visits to Zion: The park’s annual visitor count more than doubled between 1979 and 1990. The Zion-Mount Carmel Highway is dotted with ...