When the United States took possession of the Louisiana country, the upper portion contained probably not more than six thousand inhabitants, about one thousand being slaves. In 1810, it had twenty thousand. A decade later, as the Territory of Missouri, it had grown to four times that number and was ready for division and statehood. A petition reached Congress in 1819, setting forth its claims. It was understood that the new State would centre about St. Louis, a thriving city of ten thousand inhabitants, situated just below the mouth of the Missouri, and that both the Northern and Southern extremes of the vast territory would be cut off. To make a proper line of demarcation, the Kentucky-Tennessee boundary of thirty-six degrees and thirty minutes was extended across the Mississippi; and the "Arkansas country," which lay to the south of it, was erected into a separate territory and given that name. A northern boundary for the proposed state was projected westwardly from near the mouth of the Des Moines River. An attempt was made by a few radicals to apply the anti-slavery clause from the North-west Territory Ordinance of 1787 to the Territory of Arkansas; but it would so manifestly destroy the balance between the sections that the project was abandoned. In time Arkansas would become a slave State. It was presumed by many Northern statesmen that the boundary line between Arkansas and Missouri would thus be accepted as a continuation of the line between the two sections, which had been extended across the continent with the movement of the people. It was begun when Pennsylvania and all States north adopted some form of emancipation for their slaves, and neither Maryland nor any State south thought best to do so. Hence the boundary line between the two States, run by the geographers, Mason and Dixon, in early days, became the first sectional line. The Ohio River was made a prolongation of the unfortunate line through the ordinance creating the North-west Territory, which forbade slavery north of the river, and the ordinance, for the South-western Territory, which forbade interference with slavery south of the river. The westward movement of population now made it necessary to extend the line across the Louisiana Purchase.