Constitutional history is the area of historical study covering both written constitutions and uncodified constitutions, and became an academic discipline during the 19th century. The Oxford Companion to Law (1980) defined it as the study of the "origins, evolution and historical development" of the constitution of a community.
The English term is attributed to Henry Hallam, in his 1827 work The Constitutional History of England. It overlaps legal history and political history. For uncodified constitutions, the status of documents seen as contributing to the formation of a constitution has an aspect of diplomatics.
