at 7' tall, I'm now thinking it's pigweed. Does it get hairy looking buds on it when it grows?
Does it get flowers on it later in the year that look like queen anne's lace? If so, it's probably hogweed. If that's what it is, be VERY CAREFUL in handling it. It's one of the nastiest plants there is in our area. Look up phylophotodermatitis (which is what you can get on contact with the skin). Not sure if you get it from the PA variety of plant but there's "Giant Hogweed" in our area. I've called the DEP and they sent someone out to check the hogweed. If it's the "Giant Hogweed" variety, they send people out for something like 7 years to try to kill it. It's that hard to kill. What I found in my area is still noxious but they won't do anything with it.