The 1840s was a decade marked by significant social, political, and economic changes in many parts of the world. In the United States, this period saw the rise of the Manifest Destiny ideology, which encouraged westward expansion. The decade also experienced the Irish Potato Famine, leading to a large wave of Irish immigrants arriving in America. In Europe, the 1840s were characterized by a series of revolutions, known as the Revolutions of 1848, where people sought more democratic rights and national independence. This decade also witnessed advancements in technology, including the growth of the railroad system, which transformed transportation and trade.