<P> Fugitives were not the only black people at risk from slavecatchers . With demand for slaves high in the Deep South as cotton was developed, strong, healthy blacks in their prime working and reproductive years were seen and treated as highly valuable commodities . Both former slaves and free blacks were sometimes kidnapped and sold into slavery, as was Solomon Northup of Saratoga Springs, New York . "Certificates of freedom," signed, notarized statements attesting to the free status of individual blacks also known as free papers, could easily be destroyed or stolen, so provided little protection to bearers . </P> <P> Some buildings, such as the Crenshaw House in far southeastern Illinois, are known sites where free blacks were sold into slavery, known as the "Reverse Underground Railroad". Under the terms of the Fugitive Slave Act of 1850, when suspected fugitives were seized and brought to a special magistrate known as a commissioner, they had no right to a jury trial and could not testify in their own behalf . Technically, they were guilty of no crime . The marshal or private slave - catcher needed only to swear an oath to acquire a writ of replevin for the return of property . </P> <P> Congress was dominated by southern Congressmen, as apportionment was based on three - fifths of the number of slaves being counted in population totals . They passed the Fugitive Slave Law of 1850 because of frustration at having fugitive slaves helped by the public and even official institutions outside the South . In some parts of the North, slave - catchers needed police protection to exercise their federal authority . Opposition to slavery did not mean that all states welcomed free blacks . For instance, Indiana, whose area along the Ohio River was settled by Southerners, passed a constitutional amendment that barred free blacks from settling in that state . </P> <P> Members of the Underground Railroad often used specific terms, based on the metaphor of the railway . For example: </P>

What were some of the routes in the underground railroad