The MAX Green Line opened on September 12, 2009 as part of a project to build two MAX extensions from the original West MAX Light Rail Line. This consisted of building the new I-205 MAX line bringing light rail service into Clackamas County for the first time, and building another alignment through downtown via the new light rail tracks along the Portland Transit Mall along 6th and 5th Avenues as a place for this MAX line (along with the Yellow Line) to service downtown. Unfortunately, this project didn’t relieve the bottleneck at the Steel Bridge that all four MAX lines must still cross via two slow moving tracks that hobbles providing high frequency service to the entire MAX system.

This 6.5 mile long I-205 MAX line runs largely along the west side of I-205 south from the Gateway Transit Center (located next to the Interchange with I-84. Unlike some freeway adjacent light rail lines the design of the line (having a multi-use path parallel to it helps as well) the line does a good job a separating itself from the freeway with decent use of grassy lined berms dividing the light rail stations from the freeway, and even some level-crossings to promote connectivity from stations into neighborhoods.

The 1.8 mile extension at the opposite end along the Portland Transit Mall is very similar to the original Blue Line sidewalk MAX stations in Downtown, except running north-south. The line also brought service closer to Amtrak at Portland Union Station.

A final notable part of the new line is that all signage at the new stations is in an updated very different format with a design of white on blue text in a more modern font, instead of White Arial lettering on a Red background.