I live in an apartment building, and my landlord has neglected to mow the back yard for quite a while now. In this time period this unknown plant that I've never seen before has grown to a height of about 38iches (965mm).
I live in Central Missouri, this is the first year I've seen this plant, either here or anywhere else in Missouri. In the first photo you should see the central part of the plant, which is the tallest, and it looks like it has a good root system going because the other leaves look like they're coming from the same system, but I'm not 100% sure because I don't know a lot about plants.
Photos: (Click to enlarge)