Never been to the Black Hills during Sturgis but my wife's sister and her family live in eastern South Dakota and 20 yrs ago we were up there for a visit when Sturgis was going on. We traveled north on I-29 through western Iowa and SE South Dakota to get there and saw dozens upon dozens of riders travelling along the interstate with us until they all turned west on I-90 in Sioux Falls. We thought it was pretty amazing BUT nothing prepared us for what we saw a few days later traveling home. My wife and kids started counted north bound Harleys that we met while we travelled south and after 10 minutes of it the number was well over 400 and they gave up counting so I know what you are talking about...