Railroad Signals: Detailed photos and descriptions of various railroad signals, including searchlight, gyralight, color light and crossing signals.

Wikipedia.com: Ralph Squillace put together a nice article on wigwag signals for this site.

THE PAUL KNUTSON RAILROAD SIGNAL COLLECTION: Paul Knutson has been collecting railroad signals for many years. Pictured on this page are some of the signals he has on display at his home. He knows where every one has come from...

RAILROAD SIGNALING AND COMMUNICATIONS: Images and Information on Railroad Signaling.

  Railroad Signals of the U.S.  A comprehensive site covering American Railroad Signals.

S.P. Historical and Technical Society: The website of the S.P. Historical and Technical Society which brings you a number of publications dealing with the history and equipment of the Southern Pacific and several of its affiliated electric railway operations.

Nor-Cal S.P. Connection: Nor-Cal SP Connection is a locomotive photo roster for the SP,SSW and DRGW
featuring over 2300 different units and growing.

Southern Pacific 5623: The official website of SP GP-9 5623. The site is put together by Howard Wise, co-owner of this prestine Black Widow geep!

Alpha Rail Net (CORP): Featuring: the SP in Oregon;  the Central Oregon and Pacific; Sumpter Valley narrow gauge;   historical photos from New York, Louisiana and North Carolina; the Southern Oregon Chapter,  and   NRHS. Several photos of Oregon wigwags are featured here.

Central California Rails:   Based in Stockton Ca. contains tons of photos and information on railroading in the Central Valley and Northern California.

Southwest Shorts:   News, photography, and information on shortline railroads of Texas and the southwestern United States.

Santa Fe Subjects: Website by Evan Werkema. The site covers a variety of Santa Fe subjects, including lists of surviving depots, preserved locomotives, pages on cowl units, and a guide to railroad airhorns.

Centerville Depot: Lots of info on another historical East Bay dept.

Santa Clara Depot and Tower: The South Bay Historical Railroad Society website with information on the depot and tower. There's also a model railroad club there.

Niles Canyon Railway (Pacific Locomotive Association): Operating rail museum in Niles Canyon on the old SP line between 
Pleasanton and Niles. Wigwags and semaphores are featured on that line!

Orange Empire Railway Museum: Huge operating railroad museum in Perris Ca. reviving the old Pacific Electric, Los Angeles
Railway and much more.

For other museum links, see the Museum Pages on this site.

Altamont Press: Daily Railroad news & Railfan Timetables.

Railpictures.net: Fine photos taken by the best photogs around the world!

Railroadinfo.com: Your online source for railroad news and information. 

Trainorders.com: You'll find a host of features that include video and sound clips, photographs, discussion forums , live chat, virtual reality scenes and the Live RailCam Network with cameras at Tehachapi and Dunsmuir on the Shasta Route in California.