I don't know either, but here's an interesting site that has a lot of wildflower pictures. Maybe its in there.

~ freshair

Here is a link that might be useful: Pictures of Wildflowers

Great website, but I didn't see it there. Bookmarked the website though, thanks!

I wonder if it's a cowpen daisy?

Are the leaves and stems rough like fine sand paper? If they are it might be an Zexmenia daisy.

Zexmenia daisy is a great little mounding plant with thick foliage, blooms continually all summer, butterflies love it, evergreen in San Antonio, and takes brutal sun without wilting.

It's planted next to the street at my house.

Here is a link that might be useful: Wedelia texana (Zexemia daisy)

Looks kinda like melampodium. There's a variety that is sold as an annual alot, but this might be the wildflower form.

I don't have it to compare, but the leaves look more like melampodium in the pictures I googled.

Here is a link that might be useful: Melampodium

I think it does look like melampodium although I sure don't remember buying that.