Seventh of 45 excerpts from Lincoln by David Herbert Donald:
Lincoln hoped he could bring the Whig Party to adopt new principles. As soon as he returned to Washington in December  -- alone this time, for Mary and the children remained in Springfield -- he saw that the central issues facing the new session of Congress were those relating to slavery and its expansion. These were not issues to which he had hitherto given much thought. He had little firsthand knowledge of slavery before he went to Washington. Except for whatever he had learned on his riverboat trips to New Orleans, he was acquainted with the South's "peculiar institution" only through his brief visits to Kentucky, where the patriarchal households of the Speeds and the Todds showed the institution in its least oppressive form. Yet he was, he said many times, "naturally anti-slavery," as his father had been. . . .
Lincoln tried to maintain [a] balance after he took his seat in the House of Representatives. He took no part in the repeated and acrimonious debates over the Wilmot Proviso, which prohibited slavery in the territories acquired as a result of the Mexican War. During his first session in Congress his primary objective was the election of a Whig President, and working closely with Southern Whigs like [Alexander] Stephens, he did not want to stir up sectional animosities.
[But] he found it harder to stay aloof in his second congressional session. Antislavery congressmen, frustrated in their repeated attempts to pass the Wilmot Proviso, now turned their energies toward ending, or at least restricting, slavery in the District of Columbia. This was a question on which Lincoln and other members of Congress had mixed feelings. On the one hand, he wished to be conciliatory toward the South, and he deplored abolitionist agitation as counterproductive. On the other, he like most other free-state men, found slavery in Washington a perpetual source of offense and of embarrassment. Every congressman had some contact with the two thousand slaves in the nation's capital. Joshua Giddings's experience was not unique. At Mrs. Sprigg's bording house he, along with the other boarders -- possibly including Lincoln -- was present when three armed men forced their way in to arrest one of the black waiters. The man had been working to purchase his freedom and had paid all but sixty dollars of the price, when his master changed his mind and ordered the police to take him into custody. Even more troubling was the slave trade in Washington. Only seven blocks from the Capitol stood the warehouse of Franklin & Armfield, the country's largest slave traders. Here, in what Lincoln called "a sort of Negro livery-stable," droves of slaves were collected, kept temporarily, and then sent on for sale in the Deep South. This notorious slave trade, which offended many Southerners as well as Northerners, was the source of repeated taunts from foreign observers who pointed out the irony of men and women being sold within sight of the Capitol of a nation dedicated to liberty.