George, I would say any person who tries to claim that "the whole purpose of the war was to free the slaves" does not understand the Civil War. That clearly was not the "whole purpose" of the war at any point---even after emancipation became a Union objective. The "whole purpose" at the outbreak of the war was whether or not Southerners would succeed in breaking from the Union (ie. achieving recognition as an independent nation).

Now, slavery was inherently involved with the conflict, for significant differences pertaining to the institution caused the sectional tension and ultimately led to secession. And after the EP, ending slavery became "part" of the Union's military purpose. But the primary objective throughout the war always focused on the matter of secession.

As for sources, I don't even know where to begin, for any good book on the outbreak and objectives of the Civil War recognizes this. But, I would definitely point to Lincoln's own words in 1861, particularly his first inaugural. In part, he said:

"Apprehension seems to exist among the people of the Southern States, that by the accession of a Republican Administration, their property, and their peace, and personal security, are to be endangered. There has never been any reasonable cause for such apprehension. Indeed, the most ample evidence to the contrary has all the while existed, and been open to their inspection. It is found in nearly all the published speeches of him who now addresses you. I do but quote from one of those speeches when I declare that "I have no purpose, directly or indirectly, to interfere with the institution of slavery in the States where it exists. I believe I have no lawful right to do so, and I have no inclination to do so." Those who nominated and elected me did so with full knowledge that I had made this, and many similar declarations, and had never recanted them. And more than this, they placed in the platform, for my acceptance, and as a law to themselves, and to me, the clear and emphatic resolution which I now read:

"'Resolved, That the maintenance inviolate of the rights of the States, and especially the right of each State to order and control its own domestic institutions according to its own judgment exclusively, is essential to that balance of power on which the perfection and endurance of our political fabric depend; and we denounce the lawless invasion by armed force of the soil of any State or Territory, no matter what pretext, as among the gravest of crimes.'"

Later in the speech he stated,

"I therefore consider that in view of the Constitution and the laws, the Union is unbroken; and to the extent of my ability I shall take care, as the Constitution itself expressly enjoins upon me, that the laws of the Union be faithfully executed in all the States. Doing this I deem to be only a simple duty on my part; and I shall perform it, so far as practicable, unless my rightful masters, the American people, shall withhold the requisite means, or in some authoritative manner, direct the contrary. I trust this will not be regarded as a menace, but only as the declared purpose of the Union that will constitutionally defend and maintain itself.

"In doing this there needs to be no bloodshed or violence; and there shall be none, unless it be forced upon the national authority. The power confided to me will be used to hold, occupy, and possess the property and places belonging to the government, and to collect the duties and imposts; but beyond what may be necessary for these objects, there will be no invasion -- no using of force against or among the people anywhere. Where hostility to the United States in any interior locality, shall be so great and so universal, as to prevent competent resident citizens from holding the Federal offices, there will be no attempt to force obnoxious strangers among the people for that object. While the strict legal right may exist in the government to enforce the exercise of these offices, the attempt to do so would be so irritating, and so nearly impracticable with all, that I deem it better to forego, for the time, the uses of such offices.

"The mails, unless repelled, will continue to be furnished in all parts of the Union. So far as possible, the people everywhere shall have that sense of perfect security which is most favorable to calm thought and reflection. The course here indicated will be followed, unless current events and experience shall show a modification or change to be proper; and in every case and exigency my best discretion will be exercised according to circumstances actually existing, and with a view and a hope of a peaceful solution of the national troubles, and the restoration of fraternal sympathies and affections."
http://showcase.netins.net/web/creative/lincoln/speeches/1inaug.htm

Lincoln made it very clear in 1861 that he had no intention of interfering with slavery where it was legally established. He was not going to go to war to end slavery. He was, however, determined to resist secession and concluded that the Union was "unbroken."

Is this along the lines of what you were looking for?