Last year, Americans marked the 150th anniversary of the beginning of the Civil War, the deadliest war in the nation's history. Until recently, historians generally were satisfied that the combined number of deaths of soldiers on both sides totaled 618,222.
William Fox and Thomas Leonard Livermore, two Union Army veterans turned amateur historians, took on the task of counting the dead. They studied battlefield reports, conscription lists, pension records, and news accounts of battles.
Their estimate of Union dead was 360,222. Because many records about the South had been destroyed, they made educated guesses about the Confederate dead -- a total they put at 258,000.
Their estimates of the war's toll was accepted for more than a century, until David Hacker, a demographic historian, figured out how to use other sets of data from that era to come up with a more-accurate count. Mr. Hacker estimated that the actual number of Civil War dead is closer to 750,000.
Using a system called the two-census method, Mr. Hacker increased the mortality count by looking at data the amateur historians missed. Mr. Hacker had the benefit of more-refined demographic science and information, thanks to the Minnesota Population Center at the University of Minnesota.
Mr. Hacker looked at Census data collected in 1860 and 1870. He refined it to exclude many demographic anomalies. He looked at Census and mortality data on both sides of those decades too.
Though his figures are far more systematic than the work of his 19th century predecessors, Mr. Hacker insists his work isn't the final word. He says more research is needed.
Still, discovering that the Civil War's toll was even worse than Americans remembered is a remarkable, if sobering, achievement. The nation is even more in debt to the soldiers who fought to end slavery and preserve the Union.
Their courage and sacrifice deserves to be honored -- and counted accurately.