- http://maps.google.com/maps?ll=40.692288,-118.218598&spn=0.004669,0.009323&t=h&z=17&om=0 maps.google.com/maps?ll=40.692288,-118.218598
- http://wikimapia.org/4874712/Callahan_Bridge wikimapia.org/4874712/Callahan_Bridge
- http://books.google.com/books?id=7POEV2_XMDQC&pg=PA224&vq=callahan+bridge&dq=callahan+bridge books.google.com -- American Trails Revisited: Following in the Footsteps of the Western Pioneers
pg 224: The Applegate-Lassen Route: ... Callahan Bridge (4 miles west of Imlay on Pioneer Road). At Callahan Bridge, the road crosses over the Humboldt River and the path of the original trail coming from the east. A historical monument is located just west of the bridge.
- http://nevada.usgs.gov/ADR/surfacewater.cfm?site_no=10333000 nevada.usgs.gov/ADR/surfacewater.cfm?site_no=10333000 -- HUMBOLDT RIVER NEAR IMLAY, NV (10333000) ... 1 mi upstream from Callahan bridge ...
http://waterdata.usgs.gov/nv/nwis/uv/?site_no=10333000 waterdata.usgs.gov/nv/nwis/uv/?site_no=10333000 -- (realtime data)