William Windom was 38 in To Kill a Mockingbird when he played the character 'Mr. Gilmer'.
That was over 61 years ago in 1962.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2012 he died aged 88, starring in 71 films in his career, 70 of those after To Kill a Mockingbird was first released. If he were alive today he would be 100.
In To Kill a Mockingbird, I think William Windom looks: