Acrisio Pires and David Lightfoot (Georgetown University) wrote on 'Syntactic Change' for the Oxford Bibliographies Online.

Linguistics began in the 19th century as a historical science, asking how languages came to be the way they are. Almost all of the work dealt with the changing pronunciation of words and “sound change” more broadly. Much attention was paid to explaining why sounds changed the way they did, and that involved developing ideas about directionality. Work on syntax was limited to compiling how different languages expressed clause types differently, notably Vergleichende Syntax der Indogermanischen Sprachen, by Berthold Delbrück. With the greatly increased attention to syntax in the latter half of the 20th century, approaches to syntactic change were enriched significantly. Most of the work on change, both generative and nongenerative, continued the 19th-century search for an inherent directionality to language change, now in the domain of syntax, but other approaches were developed seeking to understand new syntactic systems arising through the contingent conditions of language acquisition.: