"Atzerodt and Powell were both arrested not far from the locations of their crimes. The angry populous of DC ensured that. Practically as soon as they were in handcuffs a death sentence was assured. Booth however was missing. President Foster rushed to organize the biggest manhunt in American history. After his swearing in he offered 100 thousand dollars cash for anyone who got Booth alive and $10,000 for any information on the conspirators. Within the next two days most people even tangentially involved in the assassinations were in cuffs and awaiting what were going to be speedy trials.
On April 23 the three bodies were prepared the largest funeral procession in American history. Millions of people turned out as to catch a glimpse. Each body would be returned to their hometowns. Thus three trains were sent off in different directions. One to New York, one to Tennessee and of course one to Illinois. Every newspaper in the north, republican leaning or democratic leaning paid their respects to the three men. In fact many southern newspapers would do the same identifying the time as one of sorrow. (Also probably hoping for some brownie points). When news of the assassinations reached the remaining confederate soldiers and officials reactions were mixed. Some saw it as dishonorable. Many commanders surrendering in the coming weeks. Others however, saw the assassinations as a blessing."
by Jack Howe, published 2002
"Even though Lee surrendered few can consider that moment to be the end of the American Civil War. For many confederate soldiers the Triple Calamity was seen as a total decapitation of the US government. Some believed that they could continue the fight. The War Department and Stanton realized this after the Battle of Columbus on April 16th. You see, pretty much all throughout April 15th the federal government was quite loud. Relaying orders to union divisions throughout the south that even though it was a time of mourning it was also a time of vengeance. These telegraphs were probably a mistake as confederate generals would also relay the information to their soldiers on the 15th and 16th. General James H. Wilson had been given a order to capture one of the last confederate supply hubs at Columbus, Georgia. He had ninety five hundred men at his command outnumbering confederate general Howell Cobbs garrison by 3:1. Yet Wilson and his men didn't capture Columbus on the 16th. They were repelled at least two times before they finally took the city on the 18th after heavy casualties. All things considered that should've been an easy battle with no less than a hundred losses.  Instead 1000 more men lost their lives.
The confederate garrison had learned of the Triple Calamity mere hours before the battle began. It seems like a mixture of Union sadness and Confederate lifted spirits cost 1000 union lives for a small town. When that news was relayed back to DC along with reports of supply line attacks and near constant calvary raids it became clear that the war would be continuing in some form or another for some time..."
From The Final Months: American Civil War April-September
By Lindsey Beck, Published 1955
"Aside from the manhunt for Booth, President Foster had a lot on his docket. First he needed a new Secretary of State. It was that particular Secretary that was needed to begin the special election process. It wasn't much of a competition of who luckily. The current assistant SoS was Frederick Seward. Though he was injured after a pistol whipping given to him by the assassin of his father, he was also the perfect choice. Foster appointed him to the vacancy and within a week the senate near unanimously approved him. Frederick had little time to mourn. After his appointment was confirmed he informed all the states in the union that a special election was to be held on the first tuesday of November and thus they should begin preparations for elections.
President Foster was rapidly approached by many political figures in congress to see what his view on reconstruction was. Foster himself was a moderate and hoped to follow the example of Lincoln. This infuriated many radical republicans who believed that Foster was nothing more than a lame duck and that 1865 was going to be a year of nothing on the issue of reconstruction. They weren't really wrong either. Foster really was hoping to kick all these issues down the road until the next president was inaugurated. He had no real intention of doing anything meaningful other than stop the government from collapsing. He essentially moved to be nice to everyone. Did the confederate states commit suicide and forfeit their right to statehood? Foster said maybe. Can former confederate states participate in the special election? Foster said absolutely not. This didn't really jive with congress.
One thing Foster did want to achieve and fast was the end of the war. On April 20th Foster met with General Ulysses S. Grant. Foster was hoping to be able to declare the war over. If he does that, then he can say anyone still holding up arms is committing full treason and won't be eligible for post war amnesty. Grant told the President that he probably couldn't take that action until General Sherman receives a full surrender from General Joseph E. Johnston's 30,000 men in North Carolina."
- From The President No One Voted For
by Kieren Hutchinson, published 1982
"General Johnston told his general staff his intent to agree to General Sherman's final terms of unconditional surrender on April 23rd. About half of his general staff agreed and half certainly did not. After a lot of back and forth, Johnston, sick of the war, left the camp with around 18 thousand of the soldiers. They accepted the terms of Sherman. He then warned the union general that around 12 thousand men wouldn't accept the offer. Sherman continued to parlay with these men for a couple weeks. By May 15th, 12 thousand was whittled down to around 8,200. Sherman thought he could have a surrender by the end of May, but with extreme pressure from the War Department and under the encouragement of General Grant, Sherman gave a final date of May 20th. If the 8,000 didn't surrender unconditionally by that day there would be a battle. This whittled 8,000 down to 6,000 and after a quick skirmish near Greensboro the Department of Tennessee fully surrendered. May 21st is considered to be the last official day of the war....
...When news reached Jefferson Davis and his few remaining cabinet members of the surrender, they had one final meeting in a friend’s house in Georgia where Davis officially declared the dissolving of the Confederate government. Davis had actually pulled together a small army with Secretary of War, John Breckinridge, and had continued fighting for around a month. After dissolving the nation he ordered his men to surrender before attempting to flee to Europe. However, both Davis and Breckinridge were caught trying to flee to Europe on May 25th. Both were taken to a jail cell in Maryland...
...fighting would continue until mid-September yet by this point, President Foster had declared an end to the war saying, "Any citizen maintaining a rebellion against the United States by July 4th is nothing more than a looter or raider and shall be dealt with as one." After the 4th, news of confederate skirmishes had mostly stopped circulating as well. Most eyes were now on the upcoming election..."
From The Final Months: American Civil War April-September
By Lindsey Beck, Published 1955
"After declaring the end of the war, the President took more concrete stances on reconstruction. First off, he made it clear that re-admission to the union was none of his business as it wouldn't be happening before the special election anyway. In the meantime, he followed congressional advice and set up a plan to establish basic military districts.  He assured the people of the south these districts were temporary. On July 30th, he offered amnesty to any soldier in the confederate army who's personal property didn't exceed $15,000. He made it clear that pardons for confederate officers were to be on a case to case basis. (Though he did offer Robert E. Lee and Joseph Johnston pardons for their timely surrenders.) He also announced that the federal government would be prosecuting certain confederate congressmen and of course they would also prosecute Jefferson Davis and his cabinet. Attorney General Bates prepared a mobilization of the Justice Department.
Controversially, Foster shut down Sherman's thirty acres and a mule plan. Saying, "No major moves such as Sherman's redistribution should be carried out until after the election." He ensured that the War Department had strong oversight over the military districts to ensure they were only keeping the peace and not much more. Foster also in tandem with allies in the moderate republican and democratic caucuses made sure every military district would have an elected council of local unionists to help advise the military administrations.
Many people even today criticize Foster's early reconstruction. It's pretty clear that he didn't want to be micromanaging reconstruction and bigger than that, didn't really want to be president. The Foster reconstruction instead delegated rebuilding to congress, the DoJ, the Department of War and anyone else he could find to keep the nation floating until March 4 1866."
From RECONSTRUCTION: A Complete History
by Doris Goodman, published 1999
Lafayette S. Foster the 17th President of the United States