Michael Scott Moore is the author of Sweetness and Blood, a book about surfing, and he’s working on a book about pirates.

When Somali pirates started making international news, journalists and politicians said, in so many words, “Forget the romance of eye patches and parrots. These guys are mean.” They are mean, and getting meaner—Jeffrey Gettleman’s terrifying piece for this magazine (“The Wages of Anarchy”) made this very point—but they’re actually not all that foreign: The seventeenth-century Christian pirates of the Caribbean resorted to murder and torture, too. They did something, moreover, that Somalia would be lucky to learn from: They helped build America.

Colonists on the Eastern seaboard in the late 1600s were a struggling, gritty people living far from civilization but near some lucrative shipping lanes, and, after the Navigation Acts especially, they turned a blind eye to violent raids taking place just past their shores. “Very great abuses have been and continue still to be practiced,” wrote the Board of Trade in London to one colonial governor in 1697, warning him that he would lose his position if he continued to tolerate pirates.

But pirates were common in those days in spite of strict letters from London. The Navigation Acts strangled so much legal trade in the colonies that many sailors had nothing much to do. “Captains without cargo and seamen without employment turned in increasing numbers to the easy lure of piracy,” writes Douglas R. Burgess, a law historian at Yeshiva University and author of a book on colonial piracy called The Pirates’ Pact. “Piracy became—and would remain—a staple of colonial commerce long after the acts themselves were revoked.”

In fact, it flourished…