This chapter begins with the established historical corpora, three of which were of particular value as adjuncts to the Bolton/Worktown Corpus (BWC) and the Mayhew Corpus (MC) for the research namely: The Corpus of Historical American English (COHA) (19th and 20th century), The Corpus of Early English Correspondence (CEEC) (15th to 17th century) and The Corpus of Early Modern English Dialogues (CED) (16th to 18th century). The value of personal letters for the study of the vernacular is also emphasised by McCafferty and Amador-Moreno who, based on their work with the Corpus of Irish English Correspondence (CORIECOR), argue that 'letters can be rich sources of vernacular language'. Speech leaves an imprint on writing. Records of spoken utterances, dialogue in drama and fiction, private letters, and other texts representing colloquial style are of great value, although they never reproduce speech in authentic form.