Published in 1776, Adam Smith's An Inquiry into the Nature and Causes of the Wealth of Nations is the founding work of modern political economy. It analysed how the division of labour raises productivity, how markets and prices coordinate self-interested exchange, and how specialisation and trade generate wealth, including the economic relationship between town and country. Smith argued that voluntary exchange under competition could allocate resources efficiently, illustrated by his famous pin-factory example. The book synthesised and systematised economic thinking for a general readership.
It supplied the economic theory of urbanisation, specialisation and land value that still informs how cities grow and concentrate activity. Its account of markets and the division of labour underpins much later thinking on agglomeration and the economic logic of cities.