understood and mostly used alongside each other within the two systems. Varieties While written American English is largely standardized across the country and spoken American English dialects are highly mutually intelligible, there are still several recognizable regional and ethnic accents and lexical distinctions. Regional accents The regional sounds of present-day American English are reportedly engaged in a complex phenomenon of "both convergence and divergence": some accents are homogenizing and leveling, while others are diversifying and deviating further away from one another. Having been settled longer than the American West Coast, the East Coast has had more time to develop unique accents, and it currently comprises three or four linguistically significant regions, each of which possesses English varieties both different from each other as well as quite internally diverse: New England, the Mid-Atlantic states (including a New York accent as well as a unique Philadelphia–Baltimore accent), and the South. As of the 20th century, the middle and eastern Great Lakes area, Chicago being the largest city with these speakers, also ushered in certain unique features, including the fronting of the vowel in the mouth toward and tensing of the vowel wholesale to . These sound changes have triggered a series of other vowel shifts in the same region, known by linguists as the "Inland North". The Inland North shares with the Eastern New England dialect (including Boston accents) a backer tongue positioning of the vowel (to ) and the vowel (to ) in comparison to the rest of the country. Ranging from northern New England across the Great Lakes to Minnesota, another Northern regional marker is the variable fronting of before , for example, appearing four times in the stereotypical Boston shibboleth Park the car in Harvard Yard. Several other phenomena serve to distinguish regional U.S. accents. Boston, Pittsburgh, Upper Midwestern, and Western U.S. accents have fully completed a merger of the vowel with the vowel ( and , respectively): a cot–caught merger, which is rapidly spreading throughout the whole country. However, the South, Inland North, and a Northeastern coastal corridor passing through Rhode Island, New York City, Philadelphia, and Baltimore typically preserve an older cot–caught distinction. For that Northeastern corridor, the realization of the vowel is particularly marked, as depicted in humorous spellings, like in tawk and cawfee (talk and coffee), which intend to represent it being tense and diphthongal: . A split of into two separate phonemes, using different