I don't know which species of butterfly you have in America so I don't know if any I say will be relevant but here goes. For nectar...cornflowers, scabious, marjoram, thyme, forget-me-nots, mint, clover, birds foot trefoil, dandelion, primrose, honesty and violets.
For food plants you will need as many different types of grasses as poss. In the vicinity of you meadow as in around the edges let brambles grow and plant buddleia, hawthorn,sloe and let some ivy grow. In your meadow plant Alchemilla mollis, stinging nettles, fennel, cardamine, hedge mustard, lucerne, cranesbill geranium, bistort, mullein, plantain and astragulus.