According to linguists who track shifts in regional dialects, the distinction between short /o/ and long open /oh/, which distinguishes cot and caught, hock and hawk, Don and dawn, is disappearing in the North American dialect. In about half of the geographic United States and all of Canada, these pairs are pronounced the same. On a phonological atlas, the merger predominates in most of the Western United States, Northeastern New England, and creeping south out of Western Pennsylvania and Canada. Most of the heavily populated areas in the North, North Midland and mid-Atlantic States and the South keep these sounds separate. Maps also show patches like the San Francisco Bay Area and Denver as islands of speakers who distinguish these sounds. Linguists note the merger is stronger in young speakers.

Source: William Labov, "The Organization of Dialect Diversity in North America." Phonological Atlas of North America. 4 October 1996. <http://www.ling.upenn.edu/phono_atlas/ICSLP4.html> (13 October 2000)

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