The Bureau of Engraving and Printing (BEP) is a government agency within the United States Department of the Treasury that designs and produces a variety of security products for the United States government, most notable of which is Federal Reserve Notes (paper money) for the Federal Reserve, the nation's central bank. In addition to paper currency, the BEP produces Treasury securities; military commissions and award certificates; invitations and admission cards; and many different types of identification cards, forms, and other special security documents for a variety of government agencies. The BEP does not produce coins; all coinage is produced by the United States Mint. With production facilities in Washington, DC, and Fort Worth, Texas, the Bureau of Engraving and Printing is the largest producer of government security documents in the United States.

Based on this passage, which department in the united states produces american currency? Let's give stream of consciousness first:
The relevant information to answer the above question is: The Bureau of Engraving and Printing (BEP) is a government agency within the United States Department of the Treasury that designs and produces a variety of security products for the United States government, most notable of which is Federal Reserve Notes (paper money) for the Federal Reserve, the nation's central bank.
So, the final answer is the United States Department of the Treasury.