 And those both are part of her prairie trilogy, correct? Well, they're not actually a prairie trilogy. That's a very stubborn phrase that it's been hard to get rid of. One of the books that's sometimes called part of the prairie trilogy, The Song of the Lark, is not set on the prairies. It's set in the Sandhills of Colorado, a very different region, not an agricultural region at all, although all three of those books do feature immigrant or the children of immigrant heroines.