The Shell sign is a historical and protected landmark found at the intersection of Memorial Drive and Magazine Street in Cambridge, and was listed on the National Register of Historic Places on June 3, 1994. In 2011, the Shell sign was replaced with an exact replica with LED lights instead of neon lights.
From the Landmark Designation Report from 1996/2002:
The neon Shell sign is a 68-foot high illuminated advertising display constructed in 1933 by the Donnelly Electric Manufacturing Company (DEMCO).
Large-scale illuminated displays intended to be seen over long distances were an innovation of the automobile era. Neon in particular gave a highly visible glow which enabled signs to be read easily by motorists driving by.
The Shell headquarters on Comm Ave had two "spectacular" illuminated displays on the roof of the building that remained in place from 1933 through 1944, when the company decided to remove the signs, possibly in response to wartime restrictions. One of the pair was re-erected in Cambridge while the other was dismantled.
At least a half dozen such signs were arrayed along the Cambridge riverfront between the Boston University and Longfellow bridges. In later years, these signs were joined by the spectacular displays of the Coca-Cola and Citgo signs on the Boston side and the river was lit nightly with the colorful reflections of industrial and commercial advertising. With the exception of the Citgo sign in Kenmore Square, the Shell sign is the only such sign to survive.
Check out a snapshot of the industrial and commercial neon advertising days of Memorial Drive. This particular photo, taken between 1954-1958, is of Richard's Drive-In.