London
There are many accents traditionally associated with London. The most well known of the London accents long ago acquired the Cockney label from London's East End, which is heard both in London itself, and across the wider South East England region more generally. The accent of a 21st-century Londoner varies widely; what is becoming more and more common amongst the under-30s however is some fusion of Cockney with a whole array of ethnic accents, in particular Caribbean, which form an accent labelled Multicultural London English (MLE). The other widely heard and spoken accent is RP (Received Pronunciation) in various forms, which can often be heard in the media and many of other traditional professions and beyond, although this accent is not limited to London and South East England, and can also be heard selectively throughout the whole UK amongst certain social groupings. Since the turn of the century the Cockney dialect is less common in the East End and has 'migrated' east to Havering and the county of Essex.
North American English regional phonology
Regional dialects in North America are historically the most strongly differentiated along the Eastern seaboard, due to distinctive speech patterns of urban centers of the American East Coast like Boston, New York City, and certain Southern cities, all of these accents historically noted by their London-like "r"-dropping (called non-rhoticity), a feature gradually receding among younger generations, especially in the South. The Connecticut River is now regarded as the southern and western boundary of the traditional New England accents, today still centered on Boston and much of Eastern New England. The Potomac River generally divides a group of Northeastern coastal dialects from an area of older Southeastern coastal dialects. All older Southern dialects, however, have mostly now receded in favor of a strongly rhotic, more unified accent group spread throughout the entire Southern United States since the late 1800s and into the early 1900s. In-between the two aforementioned rivers, some other variations exist, most famous among them being New York City English.