In my opinon i think it would be in the 1850s because at that time The 1850 Fugitive Slave Act allowed fugitive and free slaves in the north to be captured and enslaved. This made Harriet’s job as an Underground Railroad conductor much harder and forced her to lead slaves further north to Canada, traveling at night, usually in the spring or fall when the days were shorter
Nevertheless, it’s believed Harriet personally led at least 70 slaves to freedom, including her elderly parents, and instructed dozens of others on how to escape on their own. She claimed, “I never ran my train off the track and I never lost a passenger.”