What is only G rated film to win the Oscar for Best Picture?

Gone with the Wind (1939) was rated G in 1971, after originally being simply "approved". As were My Fair Lady (1964), Ben-Hur (1959), Gigi (1958) and Around the World in 80 Days (1956).

I guess the truly G-rated movies that have won were The Sound of Music (1965) and Oliver! (1968). I don't know what their rating would be today.

So- you decide which was first and last.