This isn't a spine or something you would read to kids, but I recommend Skeletons on the Zahara by Dean King. It is about Capt James Riley who was captured off the coast of NorthWest Africa and enslaved by the Tuareg. He was redeemed (pretty miraculously) a little over a year later. He went on to write his memoirs, and what is utterly fascinating to me is that Abraham Lincoln lists it as one (among others) of the most formative books he read as a child. It helped form his views against slavery. Riley's experiences, I believe, helped somehow lead to the abolishment of slavery in the US. I wrote an age-appropriate story for my kids based on James Riley and we studied him and Harriet Tubman back to back. My kids also know that they have ancestors who were transported as war criminals during the Scottish Uprisings and were enslaved for a period of time. And I don't intend for any of that to diminish (later) studies of the horrors of the transcontinental slave trade (which was on another scale with regards to pure numbers of individuals involved.) It was important to me that my kids understand that it is wrong for any human to subjugate another human based on any reason whatsoever. It's a big picture item for me, especially around an issue that weighs so heavily on European American consciences. For elementary, that's the take-away message I want them to get: Humans have been doing crappy things to "other" humans since forever, but we can do our little part in our time and place (just as these courageous historical figures did) to see and treat all humans as One. I would recommend supplementing a regular US spine, like the Story of US, with stories, vignettes even, of the sorts of things you are interested in sharing with your kids--- all with a light touch.