This article provides a brief history of the development of library subject guides (often referred to as pathfinders) from the late 1800s to the present. During this period, subject guides have changed both their focus and format. The needs of academic institutions at the turn of the 20th century were very different than they are today, and technology that was non-existent then has become ubiquitous. Much can be learned from studying the evolution of these important library tools and looking to the future as they mature even further. (Contains 37 notes.)