During the Civil War, after issuing the
Emancipation Proclamation, President Lincoln called for a “National Day of
Humiliation, Fasting and Prayer for March 30, 1863, stating:
“It is the duty of nations…to own their dependence upon the overruling power of God, to confess their sins…with assured hope that enuine repentance will lead to mercy…The awful calamity of civil war… may be but a punishment inflicted upon us for our presumptuous sins.” Lincoln continued: “We have been the recipients of the choicest bounties of Heaven…We have grown in numbers, wealth and power as no other nation has ever grown. But we have forgotten God. We have forgotten the gracious Hand which preserved us in peace, and multiplied and enriched and strengthened us; and we have vainly imagined, in the deceitfulness
of our hearts, that all these blessings were produced by some superior wisdom and virtue of our own.” Lincoln concluded: “Intoxicated with unbroken success, we have become too self-sufficient to feel the necessity of redeeming and preserving grace, too proud to pray to the God that made us! “It behooves us then to humble ourselves before the offended Power, to confess our national sins and to pray for…forgiveness.”
http://www.dayofrepentance.org/proclamation-from-abraham-lincoln/