Through multiple revolutions people have adapted to and affected their environments. As civilizations settled, new advances in agriculture and tools were made to allow for a less-nomadic society. Through advances such as iron tools and food stock, civilizations settled creating the basis for large empires to come later. Also through the innovation of weapons and armor, empires were able to better control and defend larger territory allowing for exponential expansion. Finally, with new advances made by different civilizations, trade increased as demand for new products from other empires grew.
The provisions of the Missouri Compromise forbidding slavery in the former Louisiana Territory north of the parallel 36°30′ north were effectively repealed by Stephen A. Douglas's Kansas–Nebraska Act of 1854.
