The Federal Reserve currently considers themselves exempt from most every FOIA request. Bravo for searching deeper! The real answer is quite elusive, if all together unknowable... The rumor is that Citi Bank currently has the most shares and JP Morgan second, with those two holding almost 3/4 of the outstanding shares!
Discussion
So according to a FOIA Citibank was the largest shareholder of the New York Regional Fed in 2019. JP Morgan was second behind them. If I’m recalling correctly they owned 46% of all shares held by the New York Regional Fed. Due to the 12 distinct regional feds it makes it much harder to get an idea of what percentage of shares a bank holds of the total shares of the Federal Reserve.
I think about these things, and then I stare at these two charts and wonder how the system has not blown up yet


So according to a FOIA Citibank was the largest shareholder of the New York Regional Fed in 2019. JP Morgan was second behind them. If I’m recalling correctly they owned 46% of all shares held by the New York Regional Fed. Due to the 12 distinct regional feds it makes it much harder to get an idea of what percentage of shares a bank holds of the total shares of the Federal Reserve.