There was a spell in the 1970s when prairie style ruled, not just in the central time zone where it originated, but from sea to shining sea. The vibe was more Stevie Nicks than Louisa May Alcott, with tiered ruffled skirts, Frye boots, and high-necked, lacy Victorian collars constituting the definitive dress-up look before disco hustled in with its Qiana and abbreviated cling.
Prairie was the very last incarnation of hippie chic styling, and the label that defined it was Gunne Sax by Jessica McClintock. The name refers to the gunny (burlap/hessian) sack border that trimmed some of the earlier models, of which many of the most collectable (and commensurately expensive) are the "black label" dresses produced solely in 1969.
Gunne Sax is still producing formal dresses, but the ones to seek out for vintage authenticity are those older ones featuring calico fabrics, velvet trims, and above all abundant lace . . . fabrics that were unlikely to have dressed the original prairie princesses, but for Amie and the rest of her 70s sisters, were heartland absolute.
(Gunne Sax dress above on Etsy here)