Advanced minus the wheel, animal husbandry, the written word, and a few other things.
They did copperwork, and built mounds in fantastic geometric shapes that acted as celestial calendars.
Our modern knowledge of the Hopewell culture is limited because of the widespread destruction of the mounds during the 18th and 19th centuries to make way for farms, forts, etc.
Much of what was left, was collected by the Smithsonian, and much of that had never been studied or displayed, remaining in storage crates somewhere.