Erigeron.

It looks a lot like some of the heath aster (Symphyotrichum ericoides or Aster ericoides) photos I find online, except it's lacking the blunt brackets below the flowers which are supposed to be markers for that species. The brackets on mine are very thin and pointy. I have another (if this is one) native Texas aster; it's purple and is also a wonderfully easy & beautiful plant. Thanks again, both of you ...I'll post the name if I ever figure out exactly what it is.

Correct, both Senecio plattensis and S.aureus are now Packera plattensis and P.aurea I beieve the plant is P.aurea -- look at the basal leaves clearly seen on "Yellow weed pt2" link above. Compare them to plattensis/aurea basal leaves (more images could be found under the old name -- Senecio aureus).

I have to agree that H. annuus is the likely ID. I've been poking around this post for a few days, and find nothing else that is a decent candidate. The H. annuus plants found in gardens always have those very large heads, large leaves, and are relatively compact in form. But wild plants are often leggy, have smaller flowers (especially in dryer climates), and have fewer & smaller leaves in the inflorescence. Check online photos, and you'll see several examples that look much like the two photos above.