The Mountains to Sound Greenway encompasses a regional trail system that offers an accessible, safe and enjoyable non-motorized route from Seattle urban areas, into the Cascade Mountains and across Washington state. A hiker or biker may travel, 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 near North Bend. From there it is possible to walk, bike or ride a horse all the way to Eastern Washington.

There are a few missing links in this connected trail network, but plans are in the works to fully realize this system:

• 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 missing link between West Lake Sammamish Parkway and East Lake Sammamish Parkway and the new Sunset Interchange.
• East Lake Sammamish Trail: King County opened the trail along the east side of Lake Sammamish, which connects to the Sammamish River Trail, Tolt Pipeline Trail and Burke Gilman Trail to the north, as well as to I-90 trails to the south. This is a crucial link to creating one of the most scenic non-motorized urban trail systems in the nation.
• High Point to Preston: WSDOT has designed a trail and is looking for funding.
• Snoqualmie Falls: From the end of the Preston-Snoqualmie Trail overlooking Snoqualmie Falls, a shared right-of-way is being explored with the Puget Sound Historic Railroad to complete a trail connection all the way to the falls.
• 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.

Dowload the I-90 Greenway Trail System Map (pdf) for an overview of regional trails.