David McCullough has stressed France’s pre-eminent role in American history for years. We would not, he has argued, have a country without the French, who have permanently and profoundly shaped us. If anyone could get away with suggesting that room be made on Mount Rushmore for Astérix it is McCullough. He seems to have had something else in mind, however. With “The Greater Journey: Americans in Paris,” he explores the intellectual legacy that France settled on its 19th-century visitors. The result is an epic of ideas, as well as an exhilarating book of spells.

The tradition began very much as a case of “Lafayette, nous voici.” The first pilgrims were nearly all single, wealthy men in their 20s, serious of purpose and ambitious by nature. A number of them had played a role in the French general’s triumphant return to America. They were provincial and inexperienced. They had never before sailed. They knew little French literature. They did not yet suspect that one could be seduced by breakfast. Following a tradition established years earlier by John Adams, they came to Paris to do their homework. Oliver Wendell Holmes, James Fenimore Cooper, Charles Sumner and Samuel F. B. Morse looked to the city as library and laboratory rather than as liberation. The idea was to settle in Paris to “study hard,” a concept that would put most junior-year-abroad programs out of business.

In two panoramic chapters, McCullough introduces us to the travelers as they prepare for their adventure. “Emotions ran high on the eve of departure,” he writes. “Melancholy and second thoughts interspersed with intense excitement were the common thing.” The trip was arduous, the French drizzle constant, and bureaucracy evidently dates to Vercingetorix. But it was a fine time to make the game-­changing discovery that the Old World really was old. There were probably fewer than a thousand Americans in the city through the 1830s. All were struck by the civility of their hosts. Wine was cheaper than milk. Though the Louvre opened to the public only on Sundays, foreigners could visit throughout the week.

One American who could reliably be found there was Samuel Morse. At his side for several hours each day was his dear friend James Fenimore Cooper, whose “Last of the Mohicans” graced every Parisian bookstore window. (As Cooper noted, the French understood that novel to be the only book published in America since the time of Ben Franklin.) McCullough devotes a chapter to Morse and Cooper — the two had met at the White House in the course of Lafayette’s visit — who attest to the transformative, transfiguring power of Paris. Morse arrived as a painter and left as an inventor. He took home with him in 1832 the germ of what would become the telegraph. With a second visit, he imported Daguerre’s ideas on photography.