a pronunciations for example in gap versus gas , further defines New York City as well as Philadelphia–Baltimore accents. Most Americans preserve all historical sounds, using what is known as a rhotic accent. The only traditional r-dropping (or non-rhoticity) in regional U.S. accents variably appears today in eastern New England, New York City, and some of the former plantation South primarily among older speakers (and, relatedly, some African-American Vernacular English across the country), though the vowel-consonant cluster found in "bird," "work," "hurt," "learn," etc. usually retains its r pronunciation, even in these non-rhotic American accents. Non-rhoticity among such speakers is presumed to have arisen from their upper classes' close historical contact with England, imitating London's r-dropping, a feature that has continued to gain prestige throughout England from the late 18th century onwards, but which has conversely lost prestige in the U.S. since at least the early 20th century. Non-rhoticity makes a word like car sound like cah or source like sauce. New York City and Southern accents are the most prominent regional accents of the country, as well as the most stigmatized and socially disfavored. Southern speech, strongest in southern Appalachia and certain areas of Texas, is often identified by Americans as a "country" accent, and is defined by the vowel losing its gliding quality: , the initiation event for a complicated Southern vowel shift, including a "Southern drawl" that makes short front vowels into distinct-sounding gliding vowels. The fronting of the vowels of , , , and tends to also define Southern accents as well as the accents spoken in the "Midland": a vast band of the country that constitutes an intermediate dialect region between the traditional North and South. Western U.S. accents mostly fall under the General American spectrum. Below, ten major American English accents are defined by their particular combinations of certain vowel sounds: General American In 2010, William Labov noted that Great Lakes, Philadelphia, Pittsburgh, and West Coast accents have undergone "vigorous new sound changes" since the mid-nineteenth century onwards, so they "are now more different from each other than they were 50 or 100 years ago", while other accents, like of New York City and Boston, have remained stable in that same time-frame. However, a General American sound system also has some debated degree of influence nationwide, for example, gradually beginning to oust the regional accent in urban areas of the South and at least