Are the under sides of the leaves covered in tiny whitish hairs? If so, I'm pretty sure about what it is. If not, no idea.

Well its white and fuzzy on the underside.

Cool, it's probably Tall Thistle (Cirsium altissimum). The basal leaves look quite a bit different than the leaves you see when the plant is flowering (the second link has pictures of the basal leaves, if you scroll down a bit).

Tall Thistle (Cirsium altissimum)

http://www.missouriplants.com/...

Thank you ,those huge leaves where throwing me off.Well since I don't want it its a weed.

Whether it is a weed or not depends on your perspective. It's a native plant and is not particularly aggressive. Tall Thistle is also beloved by bees, butterflies, and goldfinches. Being a thistle, it often inspires a negative reaction in people though. Just depends on where it's growing and whether you can tolerate a thistle there.

The leaves remind me of Silphium. Their are several species that grow in Missouri.

http://bonap.org/BONAPmaps2010...

Silphiums don't have spines along the edges of their leaves, though, and the undersides are not tomentose.