President Obama pays tribute to his predecessor Abraham Lincoln
Events are being held across the US to mark 200 years since former President Abraham Lincoln was born.
Speaking at a bicentennial celebration at the Capitol, President Barack Obama said he felt "a special gratitude" to Lincoln, who fought to end slavery.
In New York, a handwritten copy of an 1864 speech delivered by Lincoln at the White House is up for auction.
A new one-cent coin is also being issued, with an image depicting the one-room cabin where Lincoln was born.
Three more one-cent coins will be released later this year, showing other scenes from his life on the reverse.
Speaking at the Capitol Rotunda at a ceremony attended by politicians and guests, Mr Obama recalled how at the end of the Civil War, Lincoln had sought reconciliation rather than revenge.
"That was the only way, Lincoln knew, to repair the rifts that had torn this country apart. It was the only way to begin the healing that our nation so desperately needed," he said.
Mr Obama urged US politicians "once again debating the critical issues of our time" to remember that, above all, they serve one country and its people.
"That is the most fitting tribute we can pay and the most lasting monument we can build to that most remarkable of men, Abraham Lincoln."
On Wednesday, Mr Obama attended Ford's Theatre - where Lincoln was assassinated in 1865 - for a gala re-opening following an 18-month restoration.
Former President Abraham Lincoln is beloved of many Americans
Speaking at that event, he reminded the crowd that Lincoln had been passionate about forging a united nation.
"For despite all that divided us - North and South, black and white - he had an unyielding belief that we were, at heart, one nation and one people," Mr Obama said.
Mr Obama has already embraced his predecessor's memory, announcing his own run for the presidency in Springfield, Illinois, Lincoln's home town, and swearing his inaugural oath on Lincoln's Bible.
He will attend a dinner honouring Lincoln in Springfield later, at which he will give the keynote address.
Events commemorating Lincoln are taking place in libraries, galleries and museums across the country.
The bicentennial has also prompted the publication of a number of new books on the president and the release of four new postage stamps featuring Lincoln.
The speech up for auction in New York, written by Lincoln to mark his re-election, remained in the family's hands until 1916.
Christie's estimates that the four-page manuscript will sell for between $3m and $4m.