The policy of maintaining an equality of slave States with free States was to be pursued, as it had already been from the foundation of the government, with unceasing vigilance and untiring energy. The balancing of forces between the new States added to the Union had been so skillfully arranged, that for a long period two States were admitted at nearly the same time,--one from the South, and one from the North. Thus Kentucky and Vermont, Tennessee and Ohio, Mississippi and Indiana, Alabama and Illinois, Missouri and Maine, Arkansas and Michigan, Florida and Iowa, came into the Union in pairs, not indeed at precisely the same moment in every case, but always with reference each to the other in the order named. On the admission of Florida and Iowa, Colonel Benton remarked that "it seemed strange that two territories so different in age, so distant from each other, so antagonistic in natural features and political institutions, should ripen into States at the same time, and come into the Union by a single Act; but these very antagonisms --that is, the antagonistic provisions on the subject of slavery-- made the conjunction, and gave to the two young States an inseparable admission." During the entire period from the formation of the Federal Government to the inauguration of Mr. Polk, the only variation from this twin birth of States--the one free, the other slave--was in the case of Louisiana, which was admitted in 1812, with no corresponding State from the North. Of the original Thirteen States, seven had become free, and six maintained slavery. Of the fifteen that were added to the Union, prior to the annexation of Texas, eight were slave, and seven were free; so that, when Mr. Polk took the oath of office, the Union consisted of twenty-eight States, equally divided between slave-holding and free. So nice an adjustment had certainly required constant watchfulness and the closest calculation of political forces. It was in pursuit of this adjustment that the admission of Louisiana was secured, as an evident compensation for the loss which had accrued to the slave- holding interest in the unequal though voluntary partition of the Old Thirteen between North and South.