This chapter begins with a brief discussion of the earliest form of patents in 500 B.C. in Greece and a pre-modern patent system in Venice, Italy in the fifteenth century, followed by a review of the origin of the United Kingdom patent system during the industrial revolution in the sixteenth century. It discusses cases and literature influential in the series of patent reforms in the nineteenth century and the development of fundamental conditions for a patent grant, including the novelty, inventive step, and sufficient disclosure for the specification as well as the introduction of the pre-grant examination on these conditions. In particular, special attention is paid to Liardet v. Johnson (1778), viewed as crucial to the development of modern patent law. The chapter also includes brief overviews of the development of patent systems in the United States, France and Germany, and patent related international agreements.