This July 1934 "The Milwaukee Magazine" has a story about the Montana Stockgrowers' Association Golden Jubilee which was held in Miles City in May of 1934. The story starts on page 3.

Milwaukee Road Archives: The Milwaukee Magazine, July 1934 edition.

Here is a picture of my Dad & Mom and older siblings at the Golden Jubilee. I wasn't born yet.

That photo looks more like the founding day of the MSGA, not the 50th anniversary!