Other publications and advertisements even song books from Yesteryear to educate men and boys on the virtues of Union Suits. It was Underwear Time:
Springtex Union Suits - "Stretches Like a Giraffe's Neck!"
Makers of B.V.D. Underwear aka Bradley, Voorhees, and Day, of course:
And TOPKIS Athletic Union Suits for Active Boys and Varsity Underwear for Older Boys: