The balance sheet of the Federal Reserve has been big in the past as can be seen in the below chart. This chart depicts the balance sheet to GDP ratio of the Federal Reserve from 1913 till 2012. The Federal Reserve was created in the year 1913.
After the crash of 1929 the balance sheet had to be increased in order to save the economy. The balance sheet to GDP ratio hit a high of 23% right at the start of World War II. Since then it had slowly trended lower to 5% of GDP until the financial crisis of 2008 hit.
Here is a chart which has the balance sheet since today. As can be seen from the chart is that the Fed’s balance sheet started rising after the financial crisis and hit a high of $ 4.4 trillion in 2014 when the Fed ended the QE program. In 2018 the Fed chose to unwind the balance sheet.
Right now the Federal Reserve balance sheet to GDP ratio sits around 18% after having hit a high of 25% in 2014. This is explained by the Fed unwinding the balance sheet from 2018 and the rise in US GDP.