each of the 12 federal reserve banks keeps an inventory of cash on hand to meet the needs of the depository institutions in its district. extended custodial inventory sites in several continents promote the use of u.s. currency internationally, improve the collection of information on currency flows, and help local banks meet the public's demand for u.s. currency. additions to that supply come directly from the two divisions of the treasury department that produce the cash: the bureau of engraving and printing, which prints currency, and the united states mint, which makes coins. most of the inventory consists of deposits by banks that had more cash than they needed to serve their customers and deposited the excess at the fed to help meet their reserve requirements.