You are farther North but it may work at your site. You’re in Iowa rather than on the East coast. The summers are hotter than on the East coast and the length of the growing season is more important than how cold it gets in the winter any way.
Goldrush was tested in central Illinois at Champaign/Urbana which is zone 5b or 6a.
I would look at this thread talking about the length of season needed for Goldrush. I think several of the posters were growing Goldrush in Iowa.