Carnegies Liked Pittsburgh Area's Growing Economy and Flexible Labor Market
(p. 32) For all its Old World charms, Dunfermline too had had its epidemics, its scavenging rodents, muddy streets, and clean water shortages. The reason why the Hogans and the Aitkins and the Carnegies and thousands like them had come to the United States in general, and the Pittsburgh area in particular, had less to do with health, hygiene, or the physical environment than with an abundance of well-paid jobs. In this respect, Pittsburgh and Allegheny City were everything that Dunfermline was not: their markets for manufactured goods were expanding rapidly, their economies were diversified, and there were no craft restrictions on the employment of skilled artisans.
Nasaw, David. Andrew Carnegie. New York: Penguin Press, 2006.
(Note: the pagination of the hardback and paperback editions of Nasaw's book are the same.)