For over a century, historians estimated that 620,000 soldiers died in the U.S. Civil War. However, research published in 2012 states that the number is closer to 750,000.
Both totals include battlefield deaths as well as those from disease, starvation and accidents. More soldiers died from disease than any other cause. The original tally came from an exhaustive study by William F. Fox and Thomas Leonard Livermore in 1889. They reviewed muster lists, battlefield reports and pension records from the two armies. The newer study used census data and included, among other things, an influx of immigrants who served in the war. Either total ranks the Civil War as the deadliest conflict in U.S. history.