Thornton Utz was an illustrator active in the 1940s and 50s. He was born in 1914 and most sources have 1999 as his year of death, though the Saturday Evening Post web site gives it as 2000.
Leif Peng blogged about Utz here, here and here. More information about him can be found here and here.
I was mostly familiar with Utz via his Saturday Evening Post covers which struck me as hack work, a gross subordination of the artist to imagined or real desiderata of the editor or his art director.
It turns out that Utz was far better than his Post covered indicated. I'm still not quite willing to place his amongst the first rank of illustrators of his era, but he surely demonstrated competence. Below are examples of his work.
Gallery
This is attributed to Utz, though there is no signature.
This seems to be a fine arts painting, not an illustration.
A nicely done portrait of the President's wife and daughter.