This is an ornamental plant called "Broom Corn". It's not really corn but a member of the sorghum family, which is another grain.
These plants grew sooooo tall. You can see in the picture, the regular sweet and field corns are planted to the left & right of the broom corn. It towers above them. I'm guessing some of the broom corn plants reached at least 14 feet tall.
I believe this type of plant was used to make old-fashioned brooms, hence the name.
They make beautiful fall decorations. I sold some at market for $1 per plant. I saved some for my front porch fall display. I also kept a lot of them to save as seed for next year.
I bought the seed from Seed Savers Exchange.