The Fed provides the figure below.
The Fed chart which goes back to 2007 does a good job of showing the spike in assets. Yet if we go back farther, say to 1996 we see that the growth seen this year is phenomenal.
(Source: Federal Reseve Statistical Release H.4.1 Factors Affecting Reserve Balances, Board of Governors of the Federal Reserve, weekly)
Sorry the data is only a few points since the Fed provides this series only as text--I have yet to read it all into a file. Yet we can still see the slow growth over that period. It took over a decade for the Fed's assets to double. Due to the Fed's litany of new lending programs including TALF, swap lines, and commercial paper, the current doubling took less than a year.