The advent of advanced electrical technology by the mid 20th allowed for an architectural fusion with what was once a secondary consideration for builders, ultimately culminating in lighting design as a profession. The development of electric light, and later, lighting design in America had many influences which drew from the realms of architectural design, engineering and the theatre and performing arts. The selected case studies characterize the overall progression occurring in the realm of integrated architectural lighting, as the architects utilized electric light as a building material. With a case study from the 1930s, one from the 1940s and one from the1950s, the lighting goals, early intent of the lighting design, installation and technical considerations of each are presented. As a secondary component to the case studies, their later (and more present day) renovations or restorations are evaluated for their relative success or failures in regards to the care and consideration of the original lighting schemes. In the revisiting of many of the interiors of this era, the now-fugitive lighting systems have been disregarded or replaced with less compatible, less complementary systems, thus destroying the ambience of the original space. If we are to accurately restore or renovate these unique American interiors, the process of researching, specifying and applying the original integrity through lighting must be achieved. Addressing these in further detail, the author has developed a series of criteria for guidelines for the preservation of early twentieth century lighting systems, which are a confluence of the previous mentioned historical research, in-depth case studies and an analysis of existing relevant guidelines.