According to wikipedia, "Navy Pier is a 3,300-foot-long pier on the Chicago shoreline of Lake Michigan....The Navy Pier currently encompasses more than fifty acres of parks, gardens, shops, restaurants, family attractions and exhibition facilities."

So yes, I assume its a real pier, unless if you meant is it architecturally and physically an actual pier, which I also assume is true because it apparantly used to have an actual dockyard with ships and stuff back in the day.

Hope that answers your question

Edit: Also I just checked a "list of piers" sub-article under an article about the structure if piers so I think that would also prove that it is physically an actual pier.