Abstract
L vocalisation is a phonetic feature found in many accents of English and other languages across the globe and it has received much attention from researchers in the past decades. In this thesis I investigate how L vocalisation has developed and spread in Great Britain and the United States. The data has been collected from the crowdsourced English Dialects app (Leeman et al., 2018) and recordings from the International Dialects of English Archive. The main focus of the analysis is on the frequency of L vocalisation in different regions in England and the United States and the phonetic environments in which L vocalisation is found in the United States. The results show that L vocalisation has likely spread through geographical diffusion in Great Britain, whereas in the United States, the feature appears to have developed independently in several accents, mostly in the Eastern half of the country. Furthermore, the thesis shows that L vocalisation is most often found before dorsal and nasal consonants and before approximants, suggesting that /l/ is more prone to vocalisation in these environments. There are several factors that contribute to differences in distribution and spreading of L vocalisation in Great Britain and the United States, ranging from geographical factors such as the size of the countries, to social factors such as social class and ethnic background.