Thanks Niranjan.
...I live in Maryland. So how do I go about looking for these here?:Niranjan.
They're everywhere that's semi-natural sparse woodlands or grasslands that aren't heavily mowed or manicured. If you live near Ellicott City, take a trip to Centennial Lake and venture down the path leading to the eastern shore of the lake, where you'll see hundreds of milkweeds (two or three species).