After passage of the Fugitive Slave Act in 1850, an escaping slave could no longer just head more or less north to cross the Ohio River or otherwise reach a non-slave state.
The task of conducting the slaves fell to careful, well-organized members of the Underground Railway. Routes were not straight line. It was mostly up to the escapee to reach the first 'station', which he did by following carefully the path passed by word of mouth among the slaves by 'travelers.'
Once the escapee reached a station, his fate was in the hands of the conductors, who laid out the route and escorted the slaves. The route never was due north, but zig-zaged according to location of safe houses or sites, and sometimes was delayed for days to a time until the route was deemed safe.
Much is written about one or two of these conductors, but there were others that were more important.
John Parker helped slaves to cross the Ohio River and passed them on to other helpers.
William Cretty of New York helped 3000.
Robert Purvis of Philadelphia is credited with transporting 9000.
William Still, also of Philadelphia, conducted many.
Others included David Ruggles, Josiah Henson, Harriet Tubman and many others whose names are buried in records or unknown.
Purvis, Still and Ruggles were African-American free men.

Routes through the northeastern states of New York, New Jersey, parts of Pennsylvania, etc., involved transit by boat, train and horse-drawn vehicles, carefully worked out to avoid enforcers of the Fugitive Slave Act.
Some 30,000 reached Canada, and others were hidden in rural areas with strong anti-slave populations.

Few slaves would be dumb enough not to know the dangers of simple-mindedly "following the drinking gourd." Getting to the first station required following careful directions which reached him by word of mouth and diagrams drawn in the dirt.