This book investigates the use of Japanese dialects brought to Hawai'i by sugar plantation immigrants between 1885 and 1924. Using both qualitative and quantitative sociolinguistic methods, it analyzes adult Japanese immigrants' oral history records that were collected from the original immigrants between 1973 and 1982 by the University of Hawai'i. The immigrants originated from different dialect speaking regions in Japan - Tohoku, Chugoku, and Kyushu. The data analyses focus on linguistic changes in light of three different frameworks - second dialect acquisition, koineization, and the founder principle. The results show that Japanese spoken by plantation immigrants did not go beyond the first of the four stages of koineization, and phonological features were the last to be acquired while the lexical features showed the earliest and highest rates of acquisition. Also, the earliest immigrants' dialect became the most significant variety in the immigrants' newly established Japanese community. Focusing on a language that is currently under-researched in the area of dialect contact and change, this book sheds new light on adult speakers' dialect contact and linguistic change phenomena.