Prairie or Sullivant’s Milkweed (Asclepias sullivantii) is worth considering as a garden alternative to Common Milkweed (A. syriaca). A key difference is that Prairie Milkweed is much less aggressive, in fact in my garden it has been fairly slow to establish.
Another difference is that the individual flowers of Prairie Milkweed are larger, and I like the pink/purple-white two tone effect. The flowers on Common Milkweed, though, are more numerous and have a stronger fragrance. The leaves of Prairie Milkweed are hairless.
Prairie Milkweed likes moist-to-medium fertile soil and full sun. In my garden it is growing a bit under 4′, shorter than Common Milkweed, but I’ve read that it tends to grow 2-3′ in the wild. It stands upright, does not need staking, and is more tolerant of dryer soils than Rose or Swamp Milkweed (A. incarnata).
In addition to being a host plant for Monarch Butterflies, Prairie Milkweed attracts many pollinators and is a valuable plant for native bees. Even so, according to the Illinois Wildflower website, the flowers do not fertilize easily. And in fact it doesn’t have any seed pods in my garden this year, but it is reblooming without any cutting back.
Illinois Wildflowers says Prairie Milkweed is “uncommon to occasional” in most Illinois counties, but not present in others. It is listed as a threatened species in Wisconsin, Minnesota, and Michigan. I have never seen it for sale at a garden center, but the online nurseries Prairie Moon and Prairie Nursery both carry it.
If you want something with a look similar to Common Milkweed but without the aggression, Prairie Milkweed is worth considering.