SR 99 formerly transitioned from a surface freeway to the double-decker elevated viaduct near South Holgate Street in SoDo, approximately north of the First Avenue South Bridge and beyond an interchange with the West Seattle Freeway near Harbor Island. The freeway then ran between the Port of Seattle's Terminal 46 and the Seattle Coast Guard Station to the west and the BNSF Railway container yard to the east. It passed a set of ghost ramps near Safeco Field that were originally planned to accommodate a freeway connection to Interstate 90 that was never built. Near CenturyLink Field, SR 99 reached the terminus of the original (and post-2011) viaduct and the south portal of the future downtown bored tunnel, using a set of diagonal ramps parallel to Railroad Way to reach the central section of the viaduct.