Washington ? The nation marked the centennial of the beginning of the Civil War in a year during which Freedom Riders pressed for integration of the South, martial law was declared in Alabama and civil rights workers were arrested in Mississippi. Sit-ins had been established as a potent weapon in the fight against segregation. And Barack Obama was born.

The United States now is making plans to mark the 150th anniversary of the war, which began in 1861. Obama now is president. The birthday of Martin Luther King Jr., who, along with 700 protesters, was arrested in Albany, Ga., in 1961, now is a federal holiday. American schoolchildren now may know as much about the civil rights movement, which is universally championed as an eloquent expression of American democracy, as they do about the Civil War, which brought about the end of slavery.

The sesquicentennial is still a year away, but the first official expression of commemoration opened this spring in Washington, where the National Archives has mounted a remarkable exhibit called “Discovering the Civil War.” The capital may seem a dispirited and dispiriting place today, but no one can fail to be encouraged by one scene on Pennsylvania Avenue, set symbolically almost halfway between the Capitol and the White House: the long, winding line of Americans waiting to get into the Archives.

This exhibit reflects not only the war that redefined the country, offering the promise of the Revolutionary years to black citizens omitted from the Revolutionary struggle for freedom. It also reflects fundamental changes in how we view the Civil War.

“There is a much greater appreciation of the African-American experience, a bigger cast of characters — we see not just generals and politicians anymore,” says Bruce Bustard, senior curator at the National Archives and the lead researcher for the exhibit. “We now see the Civil War with women, with different immigrant groups, with Southerners who didn’t support the Confederacy, and men who were substitutes and paid by someone else to take their place.”

But in one form or another, the Civil War has always been with us. It dominated the politics of the 1870s and the decades that followed; its generals provided five American presidents; and its lessons inspired Dwight D. Eisenhower, who drew on the experience of Gen. George G. Meade at Gettysburg to shape his military decisions in Europe in 1944.

The Civil War stands as evidence that history is not immutable but changeable. Today’s rendering of the Civil War is different from 1961’s Civil War, which was different from 1861’s Civil War, and not only because in 1961 and 2010 we know how it turned out. The Civil War helps explain how we turned out.

“A lot of people didn’t like Abraham Lincoln after the Civil War,” says Gabor Boritt, among the most distinguished historians of the war. “For a long time he was unacceptable in many circles. But by 1961 he was regarded as a great president. The big difference is our attitudes about race. The civil rights movement was in its early days. The really important period hadn’t yet occurred. That changed all our perspectives.”

Perhaps it was the coincidence of the calendar, perhaps it was the maturing of a hundred years of frustration, but the 100th anniversary of the Civil War in 1961 came at a peculiarly difficult time in American race relations.

In the year of the 100th anniversary, Montgomery, Ala., the first capital of the Confederacy, mounted a weeklong pageant marking the founding of the Confederacy and the inauguration of Jefferson Davis as president, an event that drew 50,000 people. Now that we are on the eve of the 150th anniversary, Montgomery is known as the site of the Montgomery bus boycott and the Rosa Parks Library and Museum sits in the center of downtown. The city boasts Maya Lin’s Civil Rights Memorial on Washington Avenue.

Robert Cook, an American who for decades taught U.S. history in Britain, studied the response of white Southerners to the Civil War centennial and noted “the connection between celebrations of the Confederacy and the contemporary threat to segregation.” From today’s perspective, it is clear that Southern politicians such as Mississippi Gov. Ross Barnett used the past “to rally popular opposition to federally sponsored integration.”

Barnett (and, later, Gov. George C. Wallace of Alabama) fought to preserve an antebellum view of race that would be discordant if not utterly illegal today. Race tensions remain, though, and while the notion of cultural and racial diversity is accepted broadly throughout the country, the Civil War — and slavery’s role in it — still provokes controversy.

Next year’s 150th anniversary commemorations represent “a prime opportunity for the president to change the narrative about slavery,” says Ronald Walters, an emeritus professor of politics at the University of Maryland and a former campaign manager for Jesse Jackson. “Some say this was a war to end slavery. Some say this was a war to save the Union. We haven’t reconciled these.”

Even so, the National Archives exhibit provides not only a lesson about the Civil War but also a lesson in how we teach lessons about the Civil War.

One of the most poignant pieces in the collection is a letter from Pvt. Benjamin Chase of the 5th New Hampshire Infantry, written on June 15, 1862.

In that letter Chase wrote he was “dreadful glad and happy” to have heard from home. He described the Battle of Fair Oaks, saying, “Oh how fast the bullets did fly.” He spoke about his location some five miles from Richmond, and about what he had learned of war and of himself in battle. “I shall know what hard living is if I ever get home,” he wrote. “I shall know what hardship is, too.”

The Civil War teaches us about hard living, and about hardship, and perhaps by remembering how we commemorated the war in 1961 — how we didn’t talk much about the causes of the war, taking refuge in battle re-enactments and costume balls and parades — we realize that perhaps we are finally close, as Chase would have put it had he not been killed six months later at Fredericksburg, to getting home.

— David Shribman is executive editor of the Pittsburgh Post-Gazette.