By the 19th century, one by one different parts of North America, recognized the liberty of black people and abolished slavery, all but the southern U.S. and its government. Both Canada and Mexico had outlawed slavery, and became refugee spots during the Underground Railroad. The northern U.S. states too had forbidden the practice, with many even including it in their state constitutions. Meanwhile, the south and the government continued supporting the matter, such as establishing the "3/5" rule, whereby despite slaves having no liberty or freedom, they still counted towards the state's population to increase their say in government matters. This great divide on the matter resulted in the inevitable conflict brewing between the North and South. The north felt such oppression was the same that they had spent years fighting against Britain for, whereas the south felt it was a necessary component to protect their economies. This dispute grew with the rise of Manifest Destiny, in which many new states and territories were added to the union. With each new addition, the question of its bearing on slavery arose, prompting fierce debate between the two sides. And with the immense chunk of land the U.S. received after the annexation of a third of Mexico, this debate was fiercer than ever. Thus arose, the premise of the Wilmot Proviso.