The concentrated of mobile tweeting in Chicago clearly outlines the economic divides of the city. For those not familiar with Chicago, wealth is concentrated in the north of downtown, with Streetervilve to Belmont making up the Gold Coast, the area near Lake Shore Drive where the richest people live and hand out.
The map above of tweeting around noon Friday in Chicago shows a concentration in the high rises and rich areas of the north with more sporadic tweeting in much of the rest of the city. Tweets concentrate very heavy in the center of cities, only a few miles outside of the main city tweeting drops radically. That is tweet locations at this scale are governed by a power law.