Short answers, pulled from the story.
Abraham Lincoln stood beneath the unfinished dome of the United States Capitol on the 4th of March 1861. This event occurred before the war began and during a time when the city felt like a small town that was virtually deserted.
Sixty-eight forts stood along the perimeter with over miles of rifle pits supporting them by 1865. Ninety-three separate batteries placed over fifteen hundred guns including mortars on this line to make the city one of the most heavily defended locations in the world.
Slavery was abolished throughout the district on the 16th of April 1862 through the Compensated Emancipation Act. Many formerly enslaved people congregated in Washington after emancipation to work constructing the ring of fortresses surrounding the city.
John Wilkes Booth shot Abraham Lincoln inside Ford's Theater on the 14th of April 1865. The president died at 7:22 the next morning in the house across the street from the theater.
Andrew Johnson declared the rebellion virtually ended on the 9th of May 1865. Three leading Union armies traveled to Washington to participate in a formal review procession starting on May 23 with the Army of the Potomac led by General George Gordon Meade.