‘I have found that a surprising amount of history can becontained in a simple cup,” Robert Hellyer writes in “Green With Milk and Sugar,” his heady brew of the intertwined history of green tea in Japan, the United States and his own family.

Mr. Hellyer, an associate professor of history at Wake Forest University, comes by his interest in tea through his paternal forebears’ long involvement in Japanese tea production and export to America, beginning with his English-born great-great grandfather Frederick Hellyer in the late...

‘I have found that a surprising amount of history can becontained in a simple cup,” Robert Hellyer writes in “Green With Milk and Sugar,” his heady brew of the intertwined history of green tea in Japan, the United States and his own family.

Mr. Hellyer, an associate professor of history at Wake Forest University, comes by his interest in tea through his paternal forebears’ long involvement in Japanese tea production and export to America, beginning with his English-born great-great grandfather Frederick Hellyer in the late 1860s. Frederick, like succeeding generations of Hellyers, came to divide his time between Riverside, Ill., and the family’s tea-processing factories in the Japanese port cities of Kobe and Shizuoka.

Although this book’s striking cover image of a rusted tea tin suggests a perky read, readers should be warned that “Green With Milk and Sugar” brims with data that is only minimally sweetened by family history (never mind the engaging techniques of narrative nonfiction). Still, there is much to savor in this heavily researched study, including archival photographs of tea fields and factories, merchants, package labels and trade advertisements.

A brief primer on the beverage derived from the domesticated tea plant Camellia sinensis sets the stage. Tea is grouped into three classes based on levels of oxidation, with green teas the least exposed, oolongs processed somewhat longer to create a yellow-brown brew, and black teas oxidized the longest. Teas in all three categories are further graded based on when the leaves are picked—with tender spring leaves most prized—and the prevalence of stems in the mix. Young hyson is the highest grade of green tea, followed by sencha. Souchong, which means “small” or “scarce,” is the choicest grade of black tea.

It may surprise readers to learn that green tea, consumed hot with milk and sugar, dominated what Mr. Hellyer dubs America’s “teaways” for some 80 years, from the 1860s through the early 1940s, particularly in the Midwest. Until then, the American penchant for tea was slaked mainly by imports from Canton. (Oolong from China, which today is consumed only by 0.5% of the U.S. population, remained New York and New England’s favorite well into the early 20th century.) The U.S. tea business underwent a sea change in 1859 after three Japanese ports were “opened” to foreign trade. The Japanese began producing Chinese-style green teas for Americans—dubbed “Japan Tea.” American tea consumption grew exponentially, and Mr. Hellyer’s ancestors were among those who helped stimulate and satisfy the demand for it. The Great American Tea Company—later expanded to the Great Atlantic & Pacific Tea Co., better known as A&P—was another prominent early trader.

Mr. Hellyer filters historical developments on both sides of the Pacific through the lens of tea—reading the tea leaves, so to speak, “to illuminate the intertwined domestic and international story.” He flags changing social trends in both America and Japan, which have rendered the partaking of tea, at different times, a cultural ritual, a late-afternoon light meal, and a predominantly female social event. While tea has become less popular than coffee in the U.S., Mr. Hellyer writes that it has come to denote “greater social sophistication.”

The effects of war and racism on the tea trade are recurring themes. Mr. Hellyer draws interesting comparisons between concurrent civil wars in America and Japan, which in the U.S. led to tariffs and a blockade of imports to Confederate states. Japan’s Meiji Restoration, which followed the defeat of the Tokugawa shogunate in 1868, led to a dislodged, unemployed samurai class, who, with the new central government’s encouragement, turned to tea farming and production for the American export market.

That market was seriously disrupted by World War II, which caused Americans to switch to black teas from India and Ceylon—resulting in a glut of green tea in Japan. This in turn led to a wartime campaign urging the Japanese to drink green tea, touted for its ability to prevent scurvy due to its high vitamin C content. To offset food shortages, tea plants were replaced with food crops. People were also urged to collect used tea leaves to create an invigorating, medicinal horse fodder.

One of the book’s darker themes addresses the use of racist tropes to manipulate the U.S. tea market—disparagements that found a receptive audience in a post-Reconstruction America already rife with racial prejudices and stereotypes. Japanese green tea gained ascendancy over Chinese teas in part because of anti-Chinese propaganda—when in fact the Japanese tea industry was built upon the expertise of Chinese tea processors. In the late 19th century, black teas from South Asia, long preferred in Britain, were “aggressively marketed through a campaign built on contempt for other Asians,” Mr. Hellyer writes. Chinese and Japanese tea production was derided as impure—tainted by unsanitary conditions and adulteration with dyes, stems and human sweat—in contrast with the purported cleanliness and efficiency of the mechanized factories in which Ceylon and India teas were “carefully prepared under white supervision.”

The Japan Central Tea Association fought back by sending representatives to promote Japanese tea and culture at American expositions and regional markets, many in the Midwest. Importers, including the Hellyers, also pushed for federal oversight and regulations to assure quality control. But the hit to Japan Tea was considerable.

Although American imports of Japanese green tea resumed after the war, by 2005 it accounted for just 12.5% of teas consumed in America and less than 1% of all U.S. tea imports, with much of it in bottles of AriZona flavored green teas. Black teas, especially the ubiquitous orange pekoe, accounted for 87% of American tea consumption, much of it in sweet iced teas. Green tea has remained dominant in Japan, although it, too, is often served in bottles and cans rather than teapots and cups.

What happened to Hellyer & Co.? Mr. Hellyer doesn’t say. But he does note that “fragrant cups of that gentle stimulant (green, oolong, and black teas—I like them all) sustained me through the writing of this book.”

Ms. McAlpin reviews books regularly for the Journal, the Christian Science Monitor, the Los Angeles Times and NPR.org.