The United States is this year marking the 150th anniversary of the Civil War.
The War between the Union and Confederate armies when Confederate forces fired on Fort Sumter on 12 April, 1861 in Charleston, South Carolina.
It lasted four years (1861-65) and claimed 620,000 lives and an unknown number of civilians. The South was defeated and slavery outlawed.
But the anniversary is also notable for a fierce, ongoing debate about why the War started.
The BBC reports a Harris Interactive poll in January found that 54% of Americans believe the South was fighting for states' rights rather than to preserve slavery, with 69% believing the North was fighting to preserve the Union rather than to abolish the institution.
The disagreement persists, despite Abraham Lincoln's observation, in his inaugural address of 1861, that slavery was ''the only substantial dispute''.