In a few weeks, an estimated 4 million visitors are expected to descend upon the picturesque southern Pennsylvania town of Gettysburg, which has a population of less than 8,000. They’re coming by the millions to commemorate the 150th anniversary of the Battle of Gettysburg, which raged across the fields, forests and rocky ridges around the town on the first three days of July 1863. It was the greatest battle of the American Civil War and the largest battle ever fought in North America.

Devil's den at Gettysburg.

Devil’s den at Gettysburg.

At Gettysburg in 1863, more than 160,000 Americans in blue and gray grappled with each other in a life-and-death struggle — not just for themselves, but for the two nations they represented. For the troops of General Robert E. Lee’s Confederate army, the struggle might have determined whether the South would win independence and nationhood; for the soldiers of General George Meade’s Federal army, the battle determined the fate and future of the American Union.

Elsewhere, Federal forces threatened to grip the South in a military stranglehold, but Lee’s masterful defense of Virginia kept the war and Southern hopes alive — and a major Confederate battlefield victory on Northern soil threatened to end the war in a Southern victory. The Battle of Gettysburg, however, concluded in a decisive Northern triumph.

The war would grind out its gory harvest for two more years, but never again would the South come so close to victory or the Union appear so close to destruction. It was a costly contest: at battle’s end, more than 51,000 Americans were counted as killed, wounded or missing. Gettysburg would prove to be the bloodiest battle of the Civil War — which was no small accomplishment in a conflict that claimed more than 620,000 American lives.

Such superlatives and drama are perhaps what will draw 4 million visitors to Gettysburg for the battle’s 150th anniversary — and perhaps what also makes the Civil War so fascinating. A century-and-a-half after the last arms were stacked and the final bugle was blown, there remains a phenomenal interest in the Civil War. Despite the allure of more modern attractions, each year millions of Americans make pilgrimages to historic sites with thoroughly American names like Chickamauga, Antietam, Kennesaw Mountain, Bull Run — and Gettysburg.

Throughout the nation, Civil War Round Table groups gather to remember what occurred at a rural peach orchard in Tennessee, an obscure cornfield in Maryland, a muddy creek in northern Virginia or a rock-strew ridge at Gettysburg. Authentically armed and uniformed “armies” of re-enactors devoted to historical detail exchange mock gunfire on battlefields of old, while collectors amass treasures of Civil War artwork, artifacts, autographs, photographs and literature.

Why does a distant conflict continue to kindle such enthusiastic fascination? Perhaps it is because the Civil War is so unique. It was not only the largest war ever waged on our continent, it was also America’s first modern war and its last “romantic” war. It was the source of remarkable wartime innovations — the first aerial reconnaissance (by balloon), the first combat between ironclad warships, the first extensive use of the telegraph in wartime, the first national income tax — and the introduction of instant coffee on a mass scale.

It was also a national event of great human drama, which made some figures into instant heroes and quickly doused the flame of fame for others. It was a war of remarkable irony — brother fighting brother, classmates contesting against each other, crucial battles which could have gone either way. It was marked by countless acts of courage, shocking occasions of cowardice, gigantic armies on the march, costly military bungling, staggering loss of life and repeated examples of selfless sacrifice. It was also a pivotal point in the nation’s history — an event that ended a near-century of debate about the right of secession by various parties, destroyed the institution of slavery in America forever and ensured the unification of the United States of America.

With so many of these superlatives, Gettysburg has come to represent the American Civil War itself. It was not just the largest and costliest battle of the Civil War, it was by most measures the decisive battle of the war. It also represents so much of what continues to make the Civil War so compelling to each new generation of Americans. It was a critical battle that could have gone either way. It is known for countless acts of heroism as well as more than a few examples of military bungling. It elevated some reputations and destroyed others.

It is marked by jaw-dropping irony, and it is replete with unforgettable incidents of pathos, drama and inspiration. All these reasons make Gettysburg the must-see historic site among the long parade of American battlefields, justify the undying fascination for the battle and the war, and make the great battle genuinely worthy of commemoration 150 years after the fields of fire and glory fell silent. But most importantly, the Battle of Gettysburg also offers all Americans — and the world — a supreme expression of American courage and sacrifice that should stand forever.

Rod Gragg, a Civil War historian, is the author of The Illustrated Gettysburg Reader: An Eyewitness History of the Civil War’s Greatest Battle,” which is newly published by Regnery Publishing.