Every summer one weed reigns supreme. Some are easy to pull up (chickweed), others are stubborn (those outrageously tough tall things that start with “A”).
This summer it’s easy. It’s whatever this nonsense is.
I fear it may be Missouri Ironweed, and the best way to tell would be to let it run rampant and see if there are showy purple flowers later.
Then of course it would be established in the yard and never go away. Missouri gardeners, let me know.