Coreopsis tinctoria?

Hmmm. The leaves are opposite, but what I read is that in Coreopsis the leaves are clustered at the base of the plant. That's not happening here. A bloom would be handy.

Ratibida species, perhaps?

LBJ Wildflower Center says Ratbida has leaves on the lower portion of the stem that are feathery and deeply cleft. Don't see that here.

All Ratibida species have alternate leaf arrangement, and their stems and leaves are covered with strigose pubescence, some hairs are glandular. Coreopsis tinctoria has glabrous leaves and stems. Their are some lower leaves, on featured plant, that look identical to C. tinctoria basal leaves. The basal leaves are for photosynthisis. Tinctoria grows rapidly and it's possible the basal leaves can dissapear when sufficiant new growth renders the basal leaves as useless. I've grown Coreopsis tinctoria many times, but I've never paid attention to the basal leaves after the plant has put on sufficiant growth. The leaves of C. tinctoria look compond, but most botanists consider them lobed, and not compound with individual leaflets, though they look like leaflets with petiolules. Ratibida leaves aren't as disected, and are more obviously lobed.

Coreopsis tinctoria basal leaves.

Leaves from featured specimen

Rafinesque named Ratibida, and noone knows why, or if 'Ratibida' means anything. Linnaeus named Coreopsis, which is Greek for 'like a bug'.

Coreopsis tribe Coreopsideae, subtribe Coreopsidinae. Ratibida tribe Heliantheae, subtribe Rudbeckiinae.

Coreopsis grandiflora has similar leaves.

My first and instant thought was "coreopsis", though I won't make a stab at the species. But Jay is correct much more than he is wrong, lol.

Looks like a coreopsis to me as well - aren't there thread-leaf and narrow leaved varieties?

You'll know for sure when it flowers, I think - and it looks like it's sending up a flower stalk to me...