During the late 18th and early 19th centuries, many countries in the Americas gained independence from European colonial powers. This led to changes in political structures and boundaries. In the United States, the Louisiana Purchase expanded its territory significantly. However, slavery remained a divisive issue and eventually led to the American Civil War between the northern and southern states from 1861-1865. Mexico also experienced political instability during this time period, including the Mexican Revolution from 1911-1920. The climate during this era was marked by the Little Ice Age, a period of global cooling that impacted societies.