The Underground Railroad consisted of a collection of secret routes and safe houses used by 19th-century enslaved American people to escape to free states and Canada with the aid of abolitionists and allies who were sympathetic to their cause.
Several earlier (pre-Revolutionary War) routes existed for getting slaves away, but the network now generally known as the Underground Railroad was formed in the early 19th century, and reached its height between 1850 and 1860. One estimate suggests that by 1850, 100,000 slaves had escaped via the “Railroad”.
Following Union victory in the Civil War, on December 6, 1865, the Thirteenth Amendment to the Constitution outlawed slavery. After its passage, in some cases the Underground Railroad operated in the opposite direction, as fugitives returned to the United States.
There were people opposed to the work done by these people as you can see in this article reprinted in the National Anti-Slavery Standard in 1858.
THE UNDERGROUND RAILROAD
From The Syracuse Courier:
“Several prominent citizens of New York are soon to be exposed as “freight agents” on the Underground Railroad. Perhaps it may leak out that some of the “conductors” reside in this city.” — Washington Union
This announcement of the Washington Union should appear under the head of “Important if true.” We are at a loss to conceive how it has been possible, thus far, for the U. S. authorities in this vicinity, or those civil magistrates of the State of New York who have taken up the oath to support the Constitution of the State of New York, and to discharge the duties of their respective offices to the best of their ability, to ignore the flagrant outrages upon the Constitution and Laws of the United States which are not only perpetrated, but publicly applauded by prominent citizens of Syracuse.