Can you give the location?There are several Erysimum species, it will help narrow down the search.

It's on a south facing hillside in Arlington, VA 22207

Compare to Erysimum capitatum. The only species native to Virginia. Could also be a non native species that escaped. Capitatum seems a match.

Hi. This flower looks like one that popped up in my yard this spring. I planted a wildflower mix last year and seeing all sorts of surprises this year.

That may be where mine came from, gumneck. I think I remember tossing out seeds from a wildflower mix years ago. Glad something finally showed up!