SAT II美国历史词汇表（7）：U-Z

U
U-boat
German submarines in World War I. German U-boat attacks against French and British passenger ships carrying American citizens provoked outrage among the American public, strengthening calls for the U.S. to join the war against the Central Powers.
Uncle Tom’s Cabin
Written by Harriet Beecher Stow and published in 1852. Uncle Tom’s Cabin portrayed the evils of the institution of slavery. The novel sold 1.2 million copies in two years and reached millions more through dramatic adaptations. Uncle Tom’s Cabin aroused sympathy for runaway slaves among all classes of Northerners and hardened many against the South’s insistence upon continuing slavery.
Underground Railroad
A network of safe houses and escorts established by Northern abolitionists to foil enforcement of the Fugitive Slave Act. The Underground Railroad helped escaped slaves reach freedom in the North and in Canada.
Underwood Tariff
Pushed through Congress by President Wilson in 1913. The Underwood Tariff reduced average tariff duties by almost 15 percent, and established a graduated income tax to cover the lost tariff revenue.
Union
A general term for the United States during the Civil War. “Union” also referred to the Northern army.
United Nations
A group of 51 countries founded the United Nations on October 24, 1945. Its central mission is to preserve peace and global stability through international cooperation and collective security. Today, the UN claims around 193 countries as members.
United Negro Improvement Association (UNIA)
Brought from Jamaica to the U.S. in 1916 by Marcus Garvey. The UNIA urged economic cooperation among African Americans.
Unrestricted submarine warfare
The German U-boat policy in which submarines attacked any ship—military, merchant, or civilian—without warning. After a period in which Germany practiced limited submarine warfare as promised by the Sussex Pledge, the resumption of unrestricted submarine warfare in January 1917 pushed the U.S. even closer to entering World War I.
Utopian communities
Small, experimental communities that sprang up in the U.S. beginning in the late 1820s. In these communities, reformers attempted to build perfect societies and present models for other communities to emulate. Most of these communities collapsed by the late 1840s.