The historical linguistic tradition dovetailed nicely with the emergence of modern dialect geography in the twentieth century. In England, Harold Orton initiated his Survey of English Dialects, collecting 404,000 items analyzed in The Linguistic Atlas of England, which he coedited with Stewart Sanderson and John Widdowson. In the United States, scholars also took to the field to develop a number of American linguistic atlases—books of data listing pronunciation features by speaker and location. More accessible to readers are the word geographies, for example, Hans Kurath’s A Word Geography of the Eastern United States, which gives the settlement and linguistic history of the eastern states, along with 162 maps of regional usages. As one might expect, many of the words were farm terms but one also finds terms for such things as truancy (play hookey, hook school, bag school, lay out). Kurath and Raven McDavid followed this with The Pronunciation of English in the Atlantic States, which also nicely describes and maps the phonetic variation in the East, with 180 maps of such things as the pronunciation of Tuesday (“twosday” or “tuseday”) and roof (with an UH or an UW sound). Craig Carver’s American Regional Dialects describes the geography and settlement history of American English using data from several linguistic atlases and from Dictionary of American Regional English (discussed above), providing a glossary of regional words and region-by-region maps representing composite dialect boundaries.
Since the mid-twentieth century, research has increasingly shifted to the sociological aspects of dialect variation—or sociolinguistics. Those interested in the intersection of sociolinguistics and the history of English will want to consult William Labov, Sharon Ash, and Charles Boberg’s The Atlas of North American English: Phonetics, Phonology, and Sound Change (ANAE). The 300-page ANAE reports on ongoing changes in the English of the United States and Canada, includes 129 four-color maps, and comes with a CD-ROM containing data files and interactive maps with sound clips. Based on a series of telephone interviews conducted in the 1990s, the ANAE focuses on active sound changes and relies on acoustic measurements rather than phonetic transcriptions. Its overview of North American dialects reaffirms some of the boundaries established by earlier studies but also describes ongoing patterns of vowel shifts in different regions, supporting the conclusion that dialect differences are becoming amplified in some areas rather than leveled out.
 Space does not permit a detailed discussion of the history of sociolinguistics. Pioneers include Joshua Fishman, Basil Bernstein, Dell Hymes, Charles Ferguson, William Labov, John Gumperz, Walt Wolfram, and Roger Shuy. For a history of sociolinguistics, see Ruth Wodak, Barbara Johnstone, and Paul E. Kerswill, eds., The SAGE Handbook of Sociolinguistics (New York: SAGE, 2010).