The Mountains to Sound Greenway encompasses a regional trail system that offers an accessible, safe, enjoyable, non-motorized route from Seattle urban areas, into the Cascade Mountains and across Washington state. A hiker or biker may travel - with a few critical gaps - beginning on the Burke Gilman, Elliott Bay, or Cedar River trails, east along I-90 to the western terminus of the John Wayne Pioneer Trail in Iron Horse State Park near North Bend. From there it is possible to walk, bike or ride a horse all the way to Eastern Washington.

Dowload the I-90 Greenway Regional Trail System Map (pdf) for an overview of regional trails and the work that is in progress to fully connect this trail network.

• Seattle: The new highway, SR 519, that connects I-90 to the Seattle waterfront near the stadiums includes a Greenway trail connection. There is a short but difficult missing link from SR 519 downtown to the beginning of the I-90 trail on Beacon Hill.
• Eastgate: The I-90 trail currently ends at Eastgate, and from there to West Lake Sammamish Parkway there is a missing link. City of Bellevue is working on a plan to make a connecting trail.
• Issaquah: There is a gap between West Lake Sammamish Parkway and East Lake Sammamish Parkway.
• High Point: WSDOT is building a new trail on the north side of I-90 between High Point and Preston. Read the WSDOT project report or take a look at construction photos.
  
• Snoqualmie: From the end of the Preston-Snoqualmie Trail overlooking Snoqualmie Falls, a shared right-of-way is being explored to complete a trail connection all the way to the falls.
• Cle Elum: There is a missing link between the Coal Mines Trail and John Wayne Pioneer Trail / Iron Horse State Park.
  
• Tolt Pipline Trail: There is a short section of the bike trail near Duvall and the Snoqualmie River that is on a stretch of busy road. Not shown on map.

Recent accomplishments in filling these gaps include an extension of the Burke Gilman Trail to Golden Gardens Park in Seattle, a new trail connection at the Sunset Interchange in Issaquah,  new trail through Marymoor Park, and the opening of the East Lake Sammamish Trail, a crucial link that helps make one of the most extensive, scenic, non-motorized urban trail systems in the nation.