As described in the last post, the Senate appointed the eight members of the Clayton Committee on Thursday July 13, 1848. The Committee performed its work expeditiously, for Senator John M. Clayton of Delaware as Chairman reported the Committee's proposed bill to the Senate less than a week later, on Wednesday July 19, 1848.
The Committee formulated its legislation in private. However, we have a reasonably good idea of the course of the Committee's deliberations. Both at the time and later Senator Clayton described the other approaches discussed and rejected before the bill took shape. In a nutshell, the four southern members – including (incredibly) John C. Calhoun of South Carolina and (ironically) David R. Atchison of Missouri – endorsed the idea of extending the Missouri Compromise line to the Pacific Ocean: slavery would be barred north of the line, and permitted (but not required) south of it. The four norther members of the committee, however, refused to acquiesce.
When he introduced the Committee's bill on July 19, 1848, Sen. Clayton related this history as follows:
[A]fter a full interchange of views, a vote was taken on a proposition moved by the Senator from Missouri, [Mr. ATCHISON,] “that the spirit of the Missouri compromise be adopted to govern the settlement of all the Territories of the United States.” On this question the committee divided, five for and three against the motion. The Senator from Indiana [Mr. BRIGHT] then moved the proposition . . . containing the words of the Missouri compromise. As the condition of the territory was now said to be different from that to which that compromise applied in 1820, a motion was made by the Senator from Kentucky [Mr. UNDERWOOD] to amend that proposition by providing that “all the territory in New Mexico and California, south of the parallel of 36° 30', shall be placed on same footing in all respects as to slavery that existed in Louisiana while it was a territory.” On this question, the committee divided, four for the motion and four against it. After the failure of this motion, the question was taken on the proposition of the Senator from Kentucky, and with a like result – the committee being again equally divided.
At this stage of the proceedings all compromise appeared to be impossible.
Six years later, debate raged in the Senate over the proposed Nebraska Bill, with northern legislators railing that the abrogation of the Missouri Compromise line was a betrayal of a fundamental compact between the sections. Presumably in that context, on March 1, 1854 Senator Clayton reportedly delivered (I cannot find the speech in the Congressional Globe; the quote below is taken from this source) a more emotionally-colored rendition of the northern members' refusal to extend the compromise line back in 1848:
Now, sir, I am compelled, in justice to both sections of the Union, to relate in your presence, you having been a member of the committee, and knowing the truth of the facts which I am about to state, what occurred in that committee. As soon as we assembled, a proposition was made by a member from the South to extend the Missouri compromise line to the Pacific. You, sir, remember it well. The vote upon it stood four northern members against it, and four southern members for it. The proposition was renewed in every form in which we could conceive it would be proper; but our northern friends rejected it as often as it was proposed. We discussed it; we entreated them to adopt it. We did not pretend that it was a constitutional measure, but it had been held by many as a compact between the North and the South, and in such an emergency as that then existing, it had been justified by the people as a measure of peace. We argued the question to show our northern friends the justice, not the constitutionality, of extending such a line to the Pacific. I remember well that I obtained a statement from the Land Office which showed the effect of it; and I thought it ought to satisfy northern gentlemen. From that statement it appeared that if the line were extended to the Pacific, the free labor of the North would have the exclusive occupation of one million six hundred thousand square miles of land in the territories outside of the states, and the South but two hundred and sixty-two thousand, in which, observe, slavery could only be tolerated in case the people residing there should allow it. The debates which followed the report of the committee fully sustain all these statements of mine. Among other things I said in a speech, delivered in the Senate, after the report, on the 3d of August, 1848, which will be found on page 1207 of the Appendix to the Congressional Globe for that session:—
"I am bound to state, and I will now do It in the presence of all the members of the committee, northern as well as southern, that in that committee the South proposed the Missouri compromise in spirit and effect; that all the territory north of 36° 30' should be free, and all south of it open to slavery, if the people there should will it."
Again, I stated at the same time:—
"The proposal of the South to run the line of 36° 30' to the Pacific would have made one million six hundred thousand square miles of the territory, lying beyond the states, on both sides the Rocky Mountains, free from slavery for ever, and would have left for African slavery south of 36° 30' parts of California and New Mexico, containing only about two hundred and seventy thousand square miles of the most worthless part of the whole country – In other words less than one-sixth in area, and less than one-twentieth in value of all the territory acquired by the common blood and treasure. The gentlemen of the committee from the North having voted down this proposal made by a southern member, there was indeed, as the gentleman from South Carolina [Mr. Calhoun] has described it, a solemn pause in that committee. All hope of amicable settlement for the moment vanished, and unnatural contention seemed likely to prevail among us. . . .
Mr. Atchison, the President, (in the chair,) here rose, and said: If the Senate will permit me, I will here state that the Senator from Delaware has, according to tho best of my recollection, substantially stated what did take place while that committee was in session.