Most Americans preserve all historical sounds, using what is known as a rhotic accent. The only traditionally "r"-dropping (or non-rhotic) regional U.S. accents are spoken in eastern New England, New York City variably, and some of the former plantation South primarily among older speakers (and consequently African-American Vernacular English variably 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".