Here is a solitary plant that I observed from June to September of last year, waiting for it to do some unique development that would give its identity away. It never happened. This year I wanted to see it in it's infancy but I can not find it. It grew alone in recently excavated/rocky/clay soil to about 5-feet in height, had a smooth square stem that became dark red toward the end of the growing season.
Thank you both. I now, (with your assistance), believe it to be either chenopodium bonus-henricus or chenopodium simplex.