Scholars have identified many different causes for the war. Among the most polarizing of the underlying issues from which other proximate causes developed was whether the institution of slavery should be retained and even expanded to other territories or whether it should be contained and eventually abolished. Since the early colonial period, slavery had played a major role in the socioeconomic system of British America and was widespread in the Thirteen Colonies at the time of the American Declaration of Independence in 1776. During and after the American Revolution, events and statements by politicians and others brought forth differences, tensions and divisions between citizens of the slave states of the Southern United States and citizens of the free states of the Northern United States (including several newly admitted Western states) over the topics of slavery. In the many decades between the Revolutionary War and the Civil War, such divisions became increasingly irreconcilable and contentious.