chapter27 By tylerpowell Period: Mar 21, 1945 to Mar 21, 1960 chapter27 Mar 21, 1948 truman adresses the nation the first time president truman adressed the nation on tv Jun 14, 1954 under god gets added to the pledge of alliegence Apr 12, 1955 polio the polio vaccine is found Mar 21, 1957 nuclear power plant shipingport pa the very first nuclear power plant built Oct 1, 1958 nasa nasa is established