Erik Gunnar Asplund’s Stockholm Public Library is considered an important building in the history of twentieth-century architecture, yet relatively few archival plans have been saved from the library’s extended design process from 1919–25 and its subsequent construction until opening in 1928. This work presents the first systematic review of the available, digitised archival plans from Sweden’s National Centre for Architecture and Design (ArkDes), and explains Asplund’s gradual design and development of the project. Subsequent alterations in the library are briefly summarised, followed by the results from an extensive 3D laser scanning process throughout and around the building as it undergoes a significant period of renovation and maintenance. The results from 3D laser scanning create the first comprehensive and detailed record of the building for supporting future research, teaching, and renovation work. This study emphasises the mutual benefits of combining historical and technological approaches, and conducting academic research in parallel with contemporary renovation projects of historical architecture.