Prefer plants native to your area. Here's an example from Missouri. Try searching (your location) + butterflies + "native plants" or similar chains.
You can also help by providing facilities such as a basking stone and puddler. Black basalt soaks up heat. It's easy to make a puddler. You might want to make a mix of sand, soil or compost, a little ash, and some mineral salt. If you mix the base and then 'flavor' separate areas with mineral salt, rotten fruit, fresh manure, etc. then you may get more different butterflies. You can make butterfly feeders from whatever you have lying around. I haven't seen suet cages used this way before, but I may try that one.