The Snohomish County Centennial Trail is a 30-mile-long (48 km) rail trail in Snohomish County, Washington, connecting the cities of Snohomish, Lake Stevens, and Arlington to Skagit County along the corridor of Washington State Route 9. The trail, administered by Snohomish County Parks and Recreation, is on the former right-of-way of the Seattle, Lake Shore and Eastern Railway and comprises a 10-foot-wide (3.0 m) non-motorized trail and a 6-foot-wide (1.8 m) equestrian trail. The first segment of the corridor was opened in 1989, the centennial of the statehood of Washington, and the final segment between Arlington and the Skagit County line was opened in 2013.

Snohomish is a city in Snohomish County, Washington, United States. The population was 10,126 at the 2020 census. It is located on the Snohomish River, southeast of Everett and northwest of Monroe. Snohomish lies at the intersection of U.S. Route 2 and State Route 9. The city's airport, Harvey Airfield, is located south of downtown and used primarily for general aviation.