It had been impossible to decide the slavery question when the Territory of Missouri was created, as was done for the land north of the Ohio, because it extended over so many degrees of latitude, covering land both favourable and hostile by climate to the system. It was thought that about one-fifth of the population was composed of slaves in 1820; but they were mostly in Arkansas Territory. From a geographical standpoint, the southern boundary of the proposed State was within half a degree of being a direct continuation of the Ohio River at its mouth. It seemed to the Northern people a most reasonable line to establish between the sections. But the Ohio pursues a south-west instead of a due west course. By following it, the South had lost two and a half degrees of territory. The Mason and Dixon line is about thirty-nine degrees and thirty minutes north latitude, while the mouth of the Ohio is at thirty-seven degrees. By extending the interstate boundary line nearest the mouth--viz., that between Kentucky and Tennessee at thirty-six degrees and thirty minutes--the slavery section would lose a strip across the Louisiana Purchase as wide as the State of Kentucky at its greatest width. Thus even the natural features of the continent seemed to cry out against drawing sectional lines for a united people. For this reason the Southern element demanded that the continuation of the line between slavery and free soil should be drawn along the northern boundary of the proposed State, which was about one degree north of the old Mason and Dixon line.