Borden Company is a dairy company that still exists today, selling milk in 9 states in the country. They had an attraction in their exhibit at the 1939 New York World’s Fair called the Rotolactor. This was a carousel with cows on it that were milked by having a hose attached to their udders. Big crowds formed when the milking would happen, but it only happened twice a day.
The mascot for Borden was, and still is, Elsie the cow. But Elsie was only on paper, not a real cow. Fairgoers wanted to know which cow at the exhibit was Elsie, so Borden picked one of the cows to be the real life Elsie. In 1940, Elsie had her own exhibit at the New York World’s Fair, which was one of the most popular at the fair. It was also in this year that she married Elmer, the popular icon on Elmer’s Glue.
image from Retro Planet
Moore's Postcard Museum 
lots of cards of Elsie & the milking machine, – on Plainsboro, NJ, cards…. where company was located. also, I have tons of World’s Fair cards. all fairs. also many Elsie advertising postcards…. someone once told me where her grave was located, but I don’t remember, – which is why Google exists. too look up stuff. One of the Plainsboro cards shows the milking machine in action…
rotolactor invented by Walker-Gordon Co of Plainsboro… that’s where you’d find more cards
There is a postcard of Elsie in her boudoir at the 1940 New York World’s Fair and also a set of Elsie comic postcards from the fair. I have images of them on my website here:
http://www.postcardy.com/article17.html
I love the comic ones! The one with her on the merry-go-round is my favorite!