"As a kid, you think it's a literal train, until at some point, hopefully a teacher or an adult corrects you and tells you how it actually worked," said Whitehead, referring to the fact that in reality, it was "a network of people" that helped slaves in America to escape from the southern states to the north.
The novel also looks at the dilemmas peculiar to the experience of a female slave.
"When a slave girl became a slave woman, she was subject to her Master's desires; she was expected to pump out babies as more slaves for her Master," pointed Whitehead, before adding, tongue firmly in cheek: "I'd written six male protagonists in a row, and I didn't want to write the same shit again".
The story required a certain maturity to handle it, and Whitehead was glad that he had waited for as long as he had to write it.
No "white babies being self-actualised against the background of slavery" may be found here, as it may be in "Gone with the Wind", he noted.
Instead, Whitehead dealt with topics such as 19th century eugenics and the forced sterilisation of black women, and drew parallels between this particular form of hegemonic injustice and others, such as the Holocaust.
"I wanted to blend reality with fictive imagination, and deploy research in an artistic way," he said.
The author said he finds himself viewing his book differently after the Trump moment in American politics.
"Police brutality was not a surprise to me," he asserted, adding that the idea connecting his novel to present day America is the basic element that "being black in the wrong place" is still dangerous and even lethal.
"The Underground Railroad" is being adapted into a web series by Barry Jenkins of Moonlight fame, and Whitehead himself will be a consultant for the show.