Dennis Hopper was 17 in Johnny Guitar when he played the character 'uncredited'.
That was over 70 years ago in 1954.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2010 he died aged 74, starring in 216 films in his career, 214 of those after Johnny Guitar was first released. If he were alive today he would be 88.
In Johnny Guitar, I think Dennis Hopper looks: