Step 1 : Introduction to the question "Who is the only President to appear on U.S. currency while still alive?"
...In 1866, Congress enacted a law banning the portrayal of living individuals on American currency. However, this precedent was surprisingly broken in 1926 when Calvin Coolidge appeared on a commemorative coin celebrating the 150th anniversary of American independence. To mark the occasion, the Philadelphia Mint issued a half dollar featuring Calvin Coolidge and George Washington on the obverse. What makes this even more remarkable is that Coolidge was not only alive but was also serving as President at the time, making him the only sitting president ever to appear on U.S. currency.