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Many roadsides have this member of the pea family planted to help with erosion control. I have lots of this crown vetch in my yard, too! Real pretty image.

This crown vetch is indeed a member of the pea family. I've seen it growing in the Midwest and in the Southeast where I live, so I take it from that, and what Wilma said, that it is a very adaptable and ubiquitous perennial plant. It brightens the roadsides in late spring and summer with its beautiful pink blossoms, and yes, it does help hold soil. (Don't plant this in your garden, though -- it is a real takeover sort!)