This image shows us what nations were potentially able to join NATO and who was able to help out the US with all their problems.
This image shows us which nations joined and at which time periods they joined.
Harry S. Truman, Dean Acheson,
One of the most important people to NATO is President Truman as he was the one who had mainly came up with it and Dean Acheson signed it and therefore NATO was born. Truman was our 33rd president.