to the regional dialects that existed in the contemporary United States. Kurath was convinced that language held a living record of events like the growth of trade and transport systems, urbanization, and population movements. By plotting regional differences in vocabulary and pronunciation on maps, Kurath and other researchers assembled what they hoped was a visual record of the social processes that had transformed American English over the past 200 years.

Each regional operation used similar techniques: a small team of linguists fanned