Beginning with the origins of their population in the seventeenth and eighteenth centuries, the author traces the Scotch-Irish development from Lowland Scotland to Northern Ireland to the American colonies.

Arriving in the East, the Scotch-Irish were characterized by other colonists as being fiery tempered, stubborn, hard drinking, and very religious, and they quickly made lasting impressions. Though the Scotch-Irish were in the minority, they managed to impact history. Most notably, they introduced the appeals system and the checks and balances system.