The house is equally significant for its role in the Underground Railroad. Hossack was a strong opponent to slavery and hid as many as 13 fleeing slaves in this house until they could safely reach the next station. These escaped slaves were in constant danger of discovery and being returned to their owners, while Hossack and others in Illinois, if caught, faced greater jeopardy than abolitionists in other states. By participating in the Underground Railroad, Hossack was violating not only the Federal Fugitive Slave Act, but also the infamous Illinois "Black Law," which forbade most African Americans from living within the State. In 1860, Hossack was one of several Ottawans charged and convicted in Federal Court in Chicago for violating the Fugitive Slave Law. The famous case involved Jim Gray, a slave who had reached Ottawa after fleeing slavery in a Southern state. During the trial Gray was abducted from the Ottawa courtroom and helped to freedom in Canada.
The John Hossack House is located at 210 W. Prospect St. in Ottawa, Illinois. It is a private residence and not open to the public.