Even though only 5% of the 18th century colonists lived in cities (and none of the cities exceeded 16,000 in 1750), the commercial capitals of coastal North America were on the cutting edge of economic, social, and political change.  It was here that the economy first changed from a barter to a commercial economy, where a competitive social order replaced one based on ascribed status, where a hierarchical and deferential polity gave way to a participatory and contentious civic life, and where factory production first began to replace small-scale artisanal production.

In the half century between 1690 and 1750 Boston, New York, and Philadelphia blossomed into commercial centers that rivaled such British provincial ports as Hull, Bristol, and Glasgow.  This urban growth reflected the development of the hinterlands to which they were commercially linked.  These seaports were also being drawn into the international market and were less self-sufficient than before.  Many of the economic decisions affecting the livelihood of people in these cities were now being made in far-off places.  The wider market was indifferent to individuals or communities, and the price of goods, labor, and land were dictated by invisible laws of the international marketplace.  So long as times were prosperous, though, people did not seem to notice or care.  Not until a crisis occurred would they begin to re-examine their new circumstances and lament the loss of their earlier values of community and concern for the "common weal."
Such a crisis occurred in Boston during the first of England's continental wars in the 18th century:  Queen Anne's War (1702-1713).  During this war, Andrew Belcher, one of the town's largest grain merchants, decided to ship large quantities of wheat to the West Indies, where prices were higher than Massachusetts.  This threatened the locals with a bread shortage.  Leading townsmen were appalled that a merchant would put profit ahead of the welfare of the community.  ordinary Bostonians took matters into their own hands.  They descended upon one of Belcher's ships, which was loaded with grain for the Indies, and sabotaged it by sawing through the rudder.  They then tried to run the ship aground in order to liberate the grain from the ship's holds.

Such food shortages rarely occurred in the American colonies, usually happening only in wartime, but when they did, urban people demanded to be fed at prices they could afford, regardless of modern notions of a free market ruled by supply and demand.

The urban social strain grew with the spread of the individualistic and entrepreneurial ethic, and became more evident in the European wars that followed Queen Anne's War.  These wars drained New England of manpower and resources during King George's War (1739-1747), when the colonists attempted to overwhelm the French enemy to the North.  But the war also offered opportunities for merchants and other to run up profits through war contracts and privateering.  This only advanced the "every man for himself" spirit and further eroded any feeling of community.  People in Boston began to turn away from their professions and became buyers and butchers of livestock.  They understood that by buying out the supplies of livestock and holding onto it for awhile, they could drive up prices.  This resulted in a kind of economic warfare between rural and urban society.

The breakdown of an interdependent economic community was equally visible in other cities during King George's War.  Food exporters in New York and Philadelphia piled up profits by illegally trading with the French and Spanish enemy in the West Indies.  They diverted food supplies for New England to the Caribbean, where the enemy paid higher prices in order to feed their slave populations.  Here was the ultimate betrayal of the public good by private interests, a betrayal reflected in the food bill of every Bostonian.  War had spurred the growing tendency of the free market, with everyone seeking to capitalize on the new opportunities for private gain.

By throwing of the governmental and ideological restraints of the past, by glorifying the concept of self-interest, the colonists were in fact bringing together what for them was the perfect relationship between a people blessed with vast areas of abundant natural resources and a people accustomed to dealing with situations on their own and developing new responses to unique situations.  The new system of values growing out of this marriage legitimated private profit-seeking, promoted the abandonment of economic regulation, and projected a future in which men's energies would be cut looses from age-old mercantilist controls instituted from above to promote the good of all.  This, many colonists argued, would produce a common good far better than the old.

Needless to say, not all colonists agreed -- particularly those who were fighting to buy bred or meat at reasonable prices.  However, these two ideas -- one, that economic life should be regulated for the common good, or that economic life should be left alone and naturally regulate itself according to supply and demand -- were competing for ascendancy in the colonial mind.  It was in the cities that shopkeepers, merchants, land speculators and others first developed a philosophical rationale to justify their new economic circumstances.  This thinking paralleled a similar train of social thought in England an Europe.  There, too, a new model of economic and social life had emerged, predicated on the notion that the market mentality was preferable to the older corporate society of persons finely attuned to the public good because the idealistic model refused to take men as they really were.  Self-denial, moral rectitude, and the subordination of private to public interests were good in theory, but in reality they acted as dead weights on the economic order.  National prosperity required a different way of thinking -- it required encouragement of acquisitive appetites and acceptance of the notion that the self-seeking drive was more powerful than institutional efforts when it came to molding people's actions.  In England, the new formula for national prosperity assumed that if each individual sought his or her own improvement, all these separate efforts would produce, through a mysterious process later described by Adam Smith as the "invisible hand," a natural harmony and a prosperous, free society.  They said that men could not be compelled to work for the good of the whole, but, if left to sort out their own wants and to pursue their own material desires in open competition, they would collectively form an impersonal market that would regulate human affairs to everyone's advantage.  Finally, in this new system, labor was more valuable than land in producing wealth.  (Given the labor situation in America, you can see why they would like this theory.)