Thanks to The Economist for pointing me to this fascinating map from Rick Aschmann.
Having lived in each corner of the country, and traveled to more than half of the states, I find accents fascinating, but never considered mapping the data. I just knew, growing up in southern New England, that "systematic r-dropping" led the word "cart" to sound like "cot" (or, more unfortunately "party" to sound like "potty.") I did not know, as Aschmann documents, that this accent type does not exist anywhere else in the world! Aschmann's work provides an interesting visual display of regional dialects, and also provides a wealth of qualitative data, including samples, on many of them.
Despite the incredible wealth of data on accents and dialects, I do think data for non-English-speaking areas are lacking. For example, the map includes Navajo, despite the fact that fewer than 400,000 people (0.13% of the nation's population) speak Navajo or another Native American language. However, the only areas labeled "Spanish Speaking" are in Mexico. Yet more than 12 percent of the U.S. population speaks Spanish. Spanish-speaking populations account for an even higher share in states along the border. Nearly 30 percent of the population age 5 and older speak Spanish as a primary language in California and Texas. Similarly, in California nearly 3 percent of the population speaks Chinese, another 2 percent speak Tagalog, and 1 percent each speak Vietnamese and Korean. (Source: U.S. Census Bureau, 2009 American Community Survey).
Click on the map, or follow the link below, to access the original.
Original map: http://aschmann.net/AmEng/#DialectDescriptionChart