This section is from the book "The National Capitol. Its Architecture Art And History", by George C. Hazelton, Jr. Also available from Amazon: The National Capitol Its Architecture Art and History.
Among the first to respond to Lincoln's call for troops after the firing on Sumter were several companies from Pennsylvania, who hastened to Washington. The Capitol was turned into temporary 16 barracks for their reception. The night they arrived, fully five hundred letters were penned in the building by the soldier-boys to the girls they had left behind them, perhaps forever, on the hills of their native State.
The Star of April 19, 1861, says : " We found company E (of this city), National Guard, the spirited volunteer company recently formed, on guard at the north wing. They are quartered in the handsome room on Revolutionary Claims. Two of the Pennsylvania companies we found quartered in the luxurious committee rooms of the north wing. The newly arrived soldiers had here Brussels carpets, marble washstands, and all that sort of thing, but seemed to think they should prefer to all this to have a bite of something to eat. They took all in good spirits except the failure in the commissariat department at their quarters. Some bacon sides had been served out in the basement (Senate kitchen refectory), where a fire had been started, and some of the soldiers were struggling with a dull knife to chip off a rasher, but nothing seemed to be in readiness for the hungry men. The three Pennsylvania companies stationed in the south wing of the Capitol were faring better, we found, as some of the Capitol employees had been laboring to get things in readiness. In the House refectories, we found the work of broiling and frying fresh and salt meat going on briskly, while numerous hogsheads and boxes containing other edibles were being depleted of their contents. Ascending to the Representatives' Hall we found nearly every seat and all the sofas of that big room occupied with the soldiers. In the centre of the room the Ringgold Artillery was located, and the wings were occupied by two other Pennsylvania companies. The lucky occupants of the sofas were taking a comfortable snooze, and those in the chairs were almost to a man engaged in writing".
The next day came the old Massachusetts Sixth, which had bravely run the gauntlet of the Baltimore mob, and they also bivouacked in the Capitol. The Star thus describes the loyal reception of that regiment by the people : " The train stopped just outside of the depot, and the troops disembarking, formed in column and marched through to New Jersey Avenue, and thence to the capitol, entering the rotunda by the East Portico. They were followed by the crowd which were now swelled to several thousands, who cheered the troops vociferously as they passed up the street. They were dressed in full winter uniform, with knapsack strapped to their back over their gray overcoats, and presented a thoroughly soldierly appearance. After halting for a while in the rotunda, the men were taken to their quarters in the new Senate chamber and the adjoining rooms. Orders were then passed among the line to stack their arms and lay aside their knapsacks, but no man was allowed to lay off his overcoat, or in any way embarrass his movements in case of an alarm. Having eaten nothing but part of a soldier's ration since ten o'clock Thursday night, the troops were nearly exhausted, and on being filed into the galleries, immediately sank down upon the cushioned seats, and forgot their fatigue and hunger in refreshing sleep".
The Seventh Regiment left New York City for Washington April 19,1861, and upon arrival reported to President Lincoln. The regiment then marched to the Capitol, where it was housed for about a week, marching, by company, to Willard's Hotel for rations. Many of the gallant Seventh recall to this-day the hard marble floors of the Capitol on which they spread their blankets. The regiment was mustered in on the campus by General McDowell.