"...a gardener who knows his flowers and is ignorant of his weeds is like half a coin, a tail without a head." Sara B. Stein
possible Spurge, there are different kinds. Euphorbia or possibly Chamaesyce spp.
Yes, I think you're right: Spotted spurge (Euphorbia maculata). Thanks NYCGardener.
Thank you! Now I know. . . it's everywhere here!
And I'll be damned, it's native! :D