This chapter mainly focuses on research into the history of standard varieties of English in Kachru’s Inner and Outer Circles. There is a long research tradition relating to the diachrony of the two major Inner Circle varieties of British and American English but it is only since about 2000 that there has been a growing number of diachronic studies on the other mother-tongue Englishes, spoken in Ireland, Canada, Australia, and New Zealand. Interest in the historical development of Outer Circle varieties (the so-called New Englishes) is even more recent, with most studies emphasizing the external history of these Englishes. Investigations of the development of linguistic structure are very rare indeed, especially regarding spoken English. One section of this chapter outlines models of the evolution of World Englishes (WEs) and their implications for research. There are also sections on existing corpora that can be used in researching the history of WEs as well as on ongoing corpus compilation and the difficulties such projects meet. Finally, the usefulness of scattered, individual early data for the reconstruction of earlier stages of WEs is illustrated.