The 80 years when the states became united

The 80 years Steven Hahn surveys in his capacious new history, “A Nation Without Borders: The United States and its World in an Age of Civil Wars, 1830-1910,” dramatically transformed American society and politics. The population grew rapidly, swelled by masses of European immigrants. America’s boundaries reached to the Pacific, linked by the distance-annihilating technologies of the transcontinental railroad and the telegraph. The economy shifted from agrarian to industrial with capitalist enterprise at its center.

“[T]he United States would, during the course of these decades, become an urban and industrial society in which state and federal governments assumed greater roles in the framing of social and economic life,” writes the award-winning New York University historian. “By 1910, as the ‘long’ nineteenth century came to a close, the United States stood as one of the most formidable nations on the globe.”

Preserving one from the many was not a smooth — or harmonious — process. A war that claimed upwards of 700,000 lives saw the abolition of slavery, a central institution in the growth of the American economy.

White settlers and the US Army clashed with Native Americans on the Plains and elsewhere. Other groups — Mormons, for example — sought to carve out their own societies, free from government interference. During the Civil War, pro-Southern agitation in the North rattled the Lincoln administration. The very nature of sovereignty, to use a favorite word of Hahn’s, was “contested” and challenged by a variety of peoples, including slaves themselves, who are central actors in the account.

This is not a typical chronological survey of American history. Hahn organizes his material around themed chapters (“Slavery and Political Culture”; ”Capitalism”) and moves back and forth in time. He has synthesized vast amounts of material and fashioned a conceptually challenging panorama. Though he offers pen portraits of Andrew Jackson, Abraham Lincoln, and other familiar political figures, this is not a story of elections — presidential races are mentioned almost in passing — but of political, geographic, and economic evolutions, which often seem more alive to the author than actual human beings.

If there is one paramount thread in an account with many, it is the outsized place of the “trans-Mississippi West” in the coming of the Civil War. Hahn opens his account in Mexico, newly independent and struggling against Indian tribes and Anglo settlers who hoped to spread slavery westward. Hahn argues, convincingly, that the United States was an empire from the start, one that endeavored to assimilate new territories. “[T]he United States wish to monopolize to themselves the privilege of colonizing . . . every . . . part of the American continent.” a British newspaper of the period observed.

This wish exerted a deforminginfluence. Hahn upgrades the Mexican-American War from mere prologue to the Civil War, aggravating as it did political schisms, to a major event, “one of the costliest, most divisive, and most politically vexing episodes in American history.” Indeed, it injected poison into the debates on the spread of slavery and whether it would proceed westward. Hahn rejects the notion that slavery was confined to the South, arguing it was a national phenomenon. Emancipation in the “free’’ North was a torturously gradual process — there were slaves in New Jersey as late as 1861 — and even free people of color risked capture by slave catchers who prowled northern cities.

Hahn’s book is a dense read buzzing with ideas. He constantly pivots from domestic to global — for example, reviewing the bloody history of antebellum Kansas, which pitted pro-slavery settlers against anti-slavery forces, Hahn also points to Cuba, which slave owners had targeted for conquest.

The War of Rebellion, as Hahn calls the Civil War, was the watershed event in the growth of American nationhood from a loose confederation of states to a single federal republic. Part of the difficulty of the task, he argues, is that it ran contrary to our nature: “secessionism was in the air from the first — the Revolution itself was a form of secessionism.” The task fell to the newly formed Republican Party and Abraham Lincoln, whose great legacy was not simply the abolition of slavery but the institution of unity.

Hahn’s account of the post-war decades showcases his impressive knowledge of black political activity, subject of his 2003 Pulitzer-Prize winning “A Nation Under our Feet.’’ Lincoln’s strong state initially backed freed people and enfranchised African Americans. But it was all short lived. Hahn shows how the “imperial arms” of the state were first used to occupy the South, then to subdue Indian populations in the West. (William T. Sherman carried on his total war methods, now against restive Comanche and Cheyennes).

Hahn also details the tensions between labor and capital that often led to violence and the sundry movements that sought alternatives to industrial capitalism. Hahn traces renewed rebellions. A resurgent South restored white rule, as the United States turned its eye toward subduing other populations abroad in the Philippines. The continent had been tamed, but the world beckoned — with modern global conflict and the rise of superpowers in the offing.

Nation Without Borders: The United States and its World in an Age of Civil Wars, 1830-1910

By Steven Hahn

Penguin, 596 pp., illustrated, $35