Rochester, Mar 3: Barely a year into the Civil War, President Abraham Lincoln suggested buying slaves for $ 400 apiece under a "gradual emancipation" plan that would bring peace at less cost than several months of hostilities.

The proposal was outlined in one of 72 letters penned by Lincoln that ended up in the University of Rochester's archives. The correspondence was digitally scanned and posted online along with easier-to-read transcriptions.

Accompanying them are 215 letters sent to Lincoln by dozens of fellow political and military leaders. They include letters from Vice President Andrew Johnson and General Ulysses S Grant, who both succeeded Lincoln in the presidency in the 12 years after his assassination in 1865.

In a letter to Illinois Sen James A McDougall dated March 14, 1862, Lincoln laid out the estimated cost to the nation's coffers of his "emancipation with compensation" proposal.

Paying slave-holders $ 400 for each of the 1,798 slaves in Delaware listed in the 1860 Census, he wrote, would come to $ 719,200 at a time when the war was soaking up $ 2 million a day.

Buying the freedom of an estimated 432,622 slaves in Delaware, Maryland, Kentucky, Missouri and Washington, DC, would cost $ 173,048,800, nearly equal to the estimated $ 174 million needed to wage war for 87 days, he added.

Lincoln suggested that each of the states, in return for payment, might set something like a 20-year deadline for abolishing slavery.