Railroad Archives Online
- CollectionD0063 - Walter W. Ainsworth Collection
- Series007 - Spokane, Portland, and Seattle Railway
- Subseries Level 1014 - Photographs
- Subseries Level 2003 - Railroads--Buildings and Structures
- Subseries Level 3007 - Tunnels
- 6 more...
- ItemWWASPSL2-021 - Spokane, Portland, and Seattle (SP&S) Cape Horn Tunnel, Cape Horn, Washington, undated
- ItemWWASPSL2-022 - Spokane, Portland, and Seattle (SP&S) Cape Horn Tunnel, Cape Horn, Washington, undated
- ItemWWASPSL2-023 - Spokane, Portland, and Seattle (SP&S) Cape Horn Tunnel, Cape Horn, Washington, March 7, 1910
- ItemWWASPSL2-024 - Spokane, Portland, and Seattle (SP&S) Cape Horn Tunnel, Cape Horn, Washington, undated
- ItemWWASPSL2-028 - Spokane, Portland, and Seattle (SP&S) Cape Horn Tunnel, Cape Horn, Washington, 1909
- ItemWWASPSL2-031 - Spokane, Portland, and Seattle (SP&S) Cape Horn Tunnel, Cape Horn, Washington, September 16, 1948
- ItemWWASPSL4-015 - Spokane, Portland, and Seattle (SP&S) Tunnel Number 5 at Cooks, Washington, undated
- ItemWWASPSL4-016 - Spokane, Portland, and Seattle (SP&S) Tunnel Number 5 at Cooks, Washington, undated
- ItemWWASPSL8-051 - Spokane, Portland, and Seattle (SP&S) Tunnel Number 3, Oregon, undated
- 9 more...