Estimates of the number of slaves who made it to freedom in the North vary considerably. It is probable, however, that perhaps one or two thousand per year were successful during the post-1830 period. Not all of them traveled along the routes of the Underground Railroad, however.

Far from being secret, [the Underground Railroad] was copiously and persistently publicized, and there is little valid evidence for the existence of a widespread underground conspiracy.

The battle to participate equally in the antislavery crusade made a number of women abolitionists acutely aware of male dominance and oppression. For them, the same principles that justified the liberation of the slaves also applied to the emancipation of women from all restrictions on their rights as citizens. In 1840, Garrison’s American followers withdrew from the first World’s Anti-Slavery Convention in London because the sponsors refused to seat the women in their delegation.

In the campaign [of 1848], both parties tried to ignore the issue of territorial slavery, but neither succeeded. A faction of the Democratic Party in New York that favored the Wilmot Proviso, called the Barnburners, broke away from the party, linked up with former Liberty party abolitionists, and courted antislavery "Conscience" Whigs to create the Free-Soil party. Declaring their dedication to "Free Trade, Free Labor, Free Speech, and Free Men," the Free-Soilers nominated Martin Van Buren on a platform opposing any extension of slavery.

Outside the public spotlight, free African Americans in the North and West contributed to the antislavery cause by quietly aiding fugitive slaves. Harriet Tubman escaped from slavery in Maryland in 1849 and repeatedly risked her freedom and her life to return to the South and escort slaves to freedom. Few matched Tubman's heroic courage, but when the opportunity arose, free blacks in the North provided fugitive slaves with food, a safe place to rest, and a helping hand.

Zachary Taylor benefited from the Democrat's alienation of key northern states over the tariff issue, from Democratic disunity over the Wilmot Proviso, and from his war-hero stature. He captured a majority of electoral votes in both North and South. Although failing to carry any state, the Free-Soil party ran well enough in the North to demonstrate the grass-roots popularity of opposition to slavery extension. Defections to the Free-Soilers, for example, probably cost the Whigs Ohio.

Risking arrest, and sometimes risking their lives, abolitionists created the Underground Railroad, a network of escape routes that provided protection and transportation for slaves fleeing north to freedom. The term railroad referred to the paths that African Americans traveled, either on foot or in wagons, across the North-South border and finally into Canada, where slave-hunters could not go. Underground meant that the operation was carried out in secret, usually on dark nights in deep woods. Men and women known as conductors acted as guides.

Many slaves who did escape got help on the Underground Railroad. This was not a real railroad, but a system of secret routes that escaping captives followed to freedom. On this ‘railroad,' the slaves were called ‘passengers.' Those who guided and transported them were ‘conductors.' The places where slaves hid along the way were called ‘stations.' People who fed and sheltered them were ‘stationmasters.' Enslaved people often used songs to signal their plan to escape.

Between 1846 and 1848 the United States successfully fought a war with Mexico that led Mexico to renounce all claims to Texas and cede its provinces of New Mexico and California to the United States. Many Americans rejoiced in the stunning victory. But some recognized that deep divisions over the status of slavery in New Mexico and California boded ill for their nation's future.

Even more disagreeable to the South was the loss of runaway slaves many of whom were assisted north by the Underground Railroad. It consisted of an informal chain of ‘stations' (anti-slavery homes), through which scores of ‘passengers' (runaway slaves) were spirited by ‘conductors' (usually white and black abolitionists) from the slave states to the free-soil sanctuary of Canada.