Griswold Signal Company

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The Griswold Signal Company was a manufacturer of traffic signals and railroad grade crossing signals based in Minneapolis, Minnesota. The company was founded by Minnesota native Frank W. Griswold, one of thirteen children born to attorney and local landowner Franklin C. Griswold.


Bobby signal[edit]

Griswold got his start in the early 1920s with the invention of the "bobby signal," a traffic signal designed for placement in the middle of an intersection that would collapse if struck by a vehicle. Many bobby signals were sold to municipalities throughout North America; this led to the development of Griswold Signal.

Rotating stop sign[edit]

The 1930s saw the invention of yet another signal. This was a unique combination of highway flasher and rotating stop sign. An approaching train would trigger not just the requisite red flashing lights and bells, but a mechanism that rotated a yellow stop sign ninety degrees to face traffic as well. (The signs eventually changed to red.)[1] This type of signal was relatively common throughout the midwestern United States; few made their way out west.

Surviving signals[edit]

Today, only three rotating stop sign signals remain in active use in the West. Two guard a crossing in Tacoma, Washington and a single Griswold guards a Union Pacific spur line on Bayshore Highway in San Jose, California; its mate was knocked down by a car in October, 2002 and was replaced by a standard flasher and electronic bell. One remaining pair guards a grade crossing on a spur in Northeast Minneapolis, Minnesota and is still in complete working order with rotating stop sign. Several remain in use in the Twin Cities area on low train traffic lines, but with only the flashers in working order- the unique rotating stop signs have been removed and disabled.

Magnetic Signal Company[edit]

The firm purchased Los Angeles-based Magnetic Signal Company in the late 1940s and moved production to Minneapolis. Magnetic Signal is the company credited with the invention of the wigwag grade crossing signal once common throughout Southern California.


Although the firm is now a part of Safetran and the name discontinued, countless Griswold Company signals of the standard variety still stand guard at crossings throughout North America.

External links[edit]


  1. ^ See a photo of one without the lights at