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)