This chapter discusses one of the principal works produced in the nineteenth century: Dr. Fred W.P. Jago’s English-Cornish dictionary. The Royal Cornwall Museum holds Jago’s working copies of his dictionary. Through six volumes, it is possible to chart Jago’s work and gain wider insights into the status of Cornish in the nineteenth century. These volumes contain a wealth of information on the social conditions of the language: subscriber lists, newspaper reviews, Jago’s correspondence regarding the history of Dolly Pentreath, and the donation of these volumes to the Royal Institution of Cornwall. Jago sought to ensure a record was kept of his working methods and decisions. This chapter offers an overview of the wider information which these working editions of Jago’s dictionary contain, and what this tells us about interest in and the status of Cornish in the 1880s.