Of all the questions which have interested and divided the people of the United States, none since the foundation of the Federal Union has been so important, so far-reaching, and so long contested as slavery. During the first half of the nineteenth century the other great national questions were nearly all economic--taxation, currency, banks, transportation, lands,--and they had a strong material basis, a flavor of self-interest; but though slavery had also an economic side, the reasons for the onslaught upon it were chiefly moral. The first objection brought by the slave-power against the anti-slavery propaganda was the cry of the sacredness of vested and property rights against attack by sentimentalists; but what dignified the whole contest was the very fact that the sentiment for human rights was at the bottom of it, and that the abolitionists felt a moral responsibility even though property owners suffered. The slavery question, which in origin was sectional, became national as the moral issues grew clearer; and finally loomed up as the dominant question through the determination of both sides to use the power and prestige of the national government. From the moral agitation came also the personal element in the struggle, the development of strong characters, like Calhoun, Toombs, Stephens and Jefferson Davis on one side; like Lundy, Lovejoy, Garrison, Giddings, Sumner, Chase, John Brown and Lincoln on the other. 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.