This a longer-than-usual origin story, but the Antietam did not have a typical journey in Congress and required a bit more discussion. I hope you have the time to read both parts of the story so that you can "experience" all of the twists and turns the coin's legislation went through.
I've written before, about how an apparent clerical error in the House kept the Battle of Antietam half dollar from being approved in the 74th Congress and thus required a bill for it to be re-introduced in the 75th Congress. You can read that post here: 1937 Battle Of Antietam 75th Anniversary - Revisited
The Battle of Antietam commemorative half dollar began its journey in Congress in March 1936 when Senator Millard Evelyn Tydings (D-MD) introduced a bill that called for up to 5,000 half dollars "in commemoration of the seventy-fifth anniversary of the Battle of Antietam." The bill was introduced on behalf of the Washington County Historical Society of Hagerstown, Maryland. The bill specified that the coins were to be struck at a single mint, all bear a "1937" date and have a coining expiration date of one year following enactment of the coin bill.
As was standard for coin bills introduced in the Senate, the bill was referred to the Senate Committee on Banking and Currency.
A week later Representative David John Lewis (D-MD) introduced a companion bill in the House of Representatives. Being a companion bill. it featured the same language and provisions as the Senate bill. It was referred to the House Committee on Coinage Weights, and Measures.
The House Committee moved much more quickly vs. the Senate Committee, reporting back on the bill about six weeks earlier. The House Committee recommended raising the mintage to 20,000 (vs. 5,000) but otherwise left the bill unaltered. The bill was passed in the House via unanimous consent, though Representatives Bertrand Hollis Snell (R-NY) and Robert Fleming Rich (R-PA) stood and voiced their displeasure and objection, in general, to Congress' continued passage of commemorative coin bills; neither, however, specifically objected to the Antietam bill. So, it moved forward.
When the Senate Committee reported its version of the bill, it recommended the coin's mintage be increased to 50,000 (at the request of Senator Tydings) and that coin orders be adjusted to a minimum of 25,000. When the Senate brought the bill up for consideration, it substituted the House bill for its own and inserted the amendments recommended by the Committee on Banking and Currency. The Senate then passed the House bill without debate and sent it back to the lower chamber for its consideration and concurrence.
It was late in the Second Session of the 74th Congress at that point and the bill was inadvertently left off the House Calendar. As a result, the House did not bring the Senate-approved version of the bill up for consideration and adjourned without taking action on it. With the adjournment, the "forgotten" bill died and would need to be re-introduced in the next Congress (i.e., the 75th) to become a reality.
In an interesting side note, on the same day his original bill was reported back from the Committee on Coinage, Weights, and Measures with a recommendation for a mintage increase to 20,000, Representative Lewis introduced a new bill that was essentially the same as his previous bill except that the specified mintage was raised to 50,000 coins (matching, but predating, the Senate Committee's recommendation). The bill was referred to the Coinage Committee, but no further action was taken on it.
Ah, for the want of a comprehensive review of pending bills!
The story continues here, in Battle of Antietam Half Dollar - Origin Story - Part II1937 Battle of Antietam 75th Anniversary Half Dollar
For other of my posts about commemorative coins and medals, including more on the history of the Battle of Antietam half dollar, see: Commems Collection.