Highway 61 never strays far from the Mississippi River, its southbound route drilling down into the heart of the troubled past of the US, through towns inextricably linked with cotton and slavery, civil war and the African-American struggle for civil rights.

The aim of my journey for the book Highway 61: Crossroads on the Blues Highway was to explore the history of that country’s most important indigenous musical form, ever mindful of Francoise N Hamlin’s words that it is the “narratives beyond the blues that are the very stories that made the blues.” What the “blues traveller” finds are stories inseparable from the broader history of African-American struggle.

On the first day of that road trip I stood with photographer Richard Brown, gazing up at the head of a prize-winning steer carved into the gothic archway over the last surviving gate to what had once been Chicago’s Union Stock Yards. It was a reminder of the “killing floors” that feature in blues songs such as Howlin’ Wolf’s Killing Floor, Skip James’s Hard Time Killing Floor Blues and Son House’s Dry Spell Blues.