Among the many weak spots in the system of slavery none gave such opportunities to Northern abolitionists as the locomotive powers of the slaves; a "thing" which could hear its owner talking about freedom, a "thing" which could steer itself Northward and avoid the "patterollers," was a thing of impaired value as a machine, however intelligent as a human being. From earliest colonial times fugitive slaves helped to make slavery inconvenient and expensive. So long as slavery was general, every slaveholder in every colony was a member of an automatic association for stopping and returning fugitives; but, from the Revolution on, the fugitives performed the important function of keeping continually before the people of the states in which slavery had ceased, the fact that it continued in other parts of the Union. Nevertheless, though between 1777 and 1804 all the states north of Maryland threw off slavery, the free states covenanted in the Federal Constitution of 1787 to interpose no obstacle to the recapture of fugitives who might come across their borders; and thus continued to be partners in the system of slavery. From the first there was reluctance and positive opposition to this obligation; and every successful capture was an object lesson to communities out of hearing of the whipping-post and out of sight of the auction-block.
In aiding fugitive slaves the abolitionist was making the most effective protest against the continuance of slavery; but he was also doing something more tangible; he was helping the oppressed, he was eluding the oppressor; and at the same time he was enjoying the most romantic and exciting amusement open to men who had high moral standards. He was taking risks, defying the laws, and making himself liable to punishment, and yet could glow with the healthful pleasure of duty done.
To this element of the personal and romantic side of the slavery contest Professor Siebert has devoted himself in this book. The Underground Railroad was simply a form of combined defiance of national laws, on the ground that those laws were unjust and oppressive. It was the unconstitutional but logical refusal of several thousand people to acknowledge that they owed any regard to slavery or were bound to look on fleeing bondmen as the property of the slaveholders, no matter how the laws read. It was also a practical means of bringing anti-slavery principles to the attention of the lukewarm or pro-slavery people in free states; and of convincing the South that the abolitionist movement was sincere and effective. Above all, the Underground Railroad was the opportunity for the bold and adventurous; it had the excitement of piracy, the secrecy of burglary, the daring of insurrection; to the pleasure of relieving the poor negro's sufferings it added the triumph of snapping one's fingers at the slave-catcher; it developed coolness, indifference to danger, and quickness of resource.