The Portland–Milwaukie Light Rail Project was the second part of the two-phased South Corridor Transportation Project that in its first phase expanded light rail services to Interstate 205 (I-205) and the Portland Transit Mall. The Portland–Milwaukie extension, which followed years of failed light rail plans for Clackamas County, began construction work in mid-2011. As part of the project, TriMet built Tilikum Crossing over the Willamette River, the first major "car-free" bridge in the United States. The extension opened to Orange Line service on September 12, 2015. The Orange Line carried an average of 11,500 daily weekday riders in September 2019.