This document provides a summary of the key developments in the field of historical linguistics. It discusses how the field originated in efforts to determine the original or pure forms of languages. Comparative methods were developed to study sound correspondences across related languages, culminating in the formulation of sound laws like Grimm's Law. Figures like Rask, Grimm, and Verner made important contributions to understanding exceptions to sound laws and the role of accent in sound changes. The Junggrammatiker school argued that sound changes are exceptionless. The document also notes debates around the family tree vs wave models of language relationships and the role of analogy vs regular sound change.