Earlier quoted context omitted.
I've been planting wildflowers at my new house as well and it's very fun to watch which plants different insects prefer. I've noticed that Monarch butterflies ignore almost all plants in my area but they love Mexican Sunflowers (Tithonia rotundifolia). I wonder how much of that is regional, since they're supposed to like Zineas and Verbena but they've shown zero interest in mine.
At my place the Monarchs (a couple weeks ago) were all attracted to a plant I haven't properly identified. It looks like queen anne's lace--crowns of many tiny, white flowers. We have a few similar-looking species in the region (Ozarks), and it could be any of them. Maybe worth a shot finding out if you want some other options for them!
[0] https://www.fs.fed.us/wildflowers/plant-of-the-week/asclepia...