In England the hymn was one Olney text among hundreds. America made it an anthem. Early American tunebooks tried it to various melodies until William Walker's Southern Harmony of 1835 fixed the words to New Britain, a pentatonic tune of folk origin, and that pairing, sung in the shape note conventions of the South, is the Amazing Grace the world knows. The stanza most congregations now sing last, when we've been there ten thousand years, is not Newton's at all, an anonymous wandering verse that Harriet Beecher Stowe attached to the hymn in Uncle Tom's Cabin, from where it entered the hymnals.
The hymn sank deep roots in the Black church, whose long metre singing traditions made it their own, and it travelled with the civil rights movement, sung in mass meetings and on marches. Judy Collins's unaccompanied recording of 1970 carried it onto the pop charts on both sides of the Atlantic, the Royal Scots Dragoon Guards' pipe band version followed, and it has become the default music of public mourning in the English speaking world, played at firefighters' and police funerals and sung by a president in Charleston in 2015. Its journey is complete in one respect above all, a hymn by a former slave trader became a treasured song of the descendants of the enslaved, grace working on the text's own terms.