But the Western expansion, though it did much to consolidate the Republic, contained in it a seed of dissension. We have seen how, in the Convention, the need of keeping an even balance between Northern and Southern sections was apparent. That need was continually forced into prominence as new States were added. The presence or absence of Negro Slavery had become the distinguishing badge of the sections; and it became the apple of discord as regards the development of the West. Jefferson had wished that Slavery should be excluded from all the territory vested in the Federal authority, but he had been overruled, and the prohibition had been applied only to the North-Western Territory out of which the States of Ohio, Indiana, and Illinois were carved. The South-West had been left open to Slavery, and it had become the custom, with the purpose of preserving the balance in the Senate, to admit Slave States and Free in pairs. This worked satisfactorily enough so long as the States claiming admission were within a well-defined geographical area. But when Missouri became sufficiently populated to be recognized as a State, there was a keen contest. Her territory lay across the line which had hitherto divided the sections. She must be either a Northern promontory projecting into the south or a Southern promontory projecting into the north. Neither section would yield, and matters were approaching a domestic crisis when Clay intervened. He was in an excellent position to arbitrate, for he came from the most northern of Southern States, and had ties with both sections. Moreover, as has been said, his talents were peculiarly suited to such management as the situation required. He proposed a settlement which satisfied moderate men on both sides, was ratified by a large majority in Congress, and accepted on all hands as final. Missouri was to enter the Union, as she apparently desired to do, as a Slave State, but to the west of her territory the line 36 deg. 30' longitude, very little above her southern border, was to be the dividing line of the sections. This gave the South an immediate advantage, but at a heavy ultimate price, for it left her little room for expansion. But one more Slave State could be carved out of the undeveloped Western Territory--that of Arkansas. Beyond that lay the lands reserved by treaty to the Indian tribes, which extended to the frontier of the Western dominions of Mexico. Clay, who, though by no means disposed to be a martyr on the question, sincerely desired to bring about the gradual extinction of Slavery, may well have deliberately planned this part of his compromise to accomplish that end. At the same time, Maine--a territory hitherto attached to Connecticut--was admitted as a Free State to balance Missouri.