Collectors of the classic-era US commemorative coin series are aware of the 1936 San Francisco-Oakland Bay Bridge Opening Half Dollar that marked the completion, dedication and opening of the two-span bridge that connected the cities of San Francisco and Oakland.
1936 San Francisco-Oakland Bay Bridge Half Dollar

I've mentioned before how the Senate bill that resulted in the "Bay Bridge" coin differed from the bill that was introduced in the House of Representatives at the same time. The House bill had a more inclusive scope, with an objective of striking coins "in commemoration of the completion of the bridges in the San Francisco Bay area."
The House bill looked to commemorate the completion of the SF-Oakland Bay Bridge, as well as the Golden Gate Bridge that was set to follow the Bay Bridge to completion; the construction timelines for the two bridges overlapped. The San Francisco-Oakland Bay Bridge opened on November 12, 1936; the Golden Gate Bridge opened about six months later on May 27, 1937.
The House bridges bill specified a mintage of 250,000, without restriction as to the number of US Mint facilities that could be engaged - P/D/S Sets would seem to have been a likely result. The coins were to be struck for the benefit of the San Francisco Bay Exposition, Incorporated and could only be ordered in batches of 25,000 or more coins.
The bill, introduced by Albert Edward Carter (R-CA), was referred to the House Committee on Coinage, Weights, and Measures. The Committee reported on the bill favorably, without amendment and recommended that it pass. The Report called out the coin's sponsor/beneficiary and noted how "the entire State [of California] will participate, with the citizens of neighboring States invited to join, in elaborate ceremonies marking the historic event. The celebration will be in the form of an exposition of trade and commerce commemorating completion of these two great arteries of transportation." The 1939-40 exposition would be named the Golden Gate International Exposition (GGIE) and be staged by the San Francisco Bay Exposition, Incorporated; see the link below for more on the half dollar proposed for the GGIE.
The House passed its "two bridges" bill, but accepted the Senate "one bridge" version of the bill as a replacement for it. The Senate bill did not include commemorating the Golden Gate Bridge among its objectives and listed a different sponsor/beneficiary - the San Francisco Clearing House Association. Net proceeds from sale of the coins were to be used to help pay for expenses related exclusively to events celebrating the opening of the SF-Oakland Bay Bridge.
I've mentioned before that I believe the House version of the bill would have been the better bill for Congress to authorize, but it appears as if the San Francisco Clearing House Association had more powerful friends in Congress than did the San Francisco Bay Exposition, Incorporated. The Clearing House got its coin approved and the Exposition company was pushed aside.
For more about the Golden Gate International Exposition coin proposal, see:
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What If? 1940 Golden Gate International ExpositionFor more about the 1936 "Bay Bridge" Half Dollar, see:
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1936 San Francisco-Oakland Bay Bridge - Redux-
Design Discussions - 1936 San Francisco - Oakland Bay Bridge OpeningFor more of my topics on commemorative coins and medals, including other What If? stories, see:
Commems Collection.