Recent photo scans from a 1960's scrap book I bought a few years ago at a swap meet. Each of the photo's have 1961 6 Day Race hand written on the back of them.  The pages of the scrap book indicate the same.  Judging from the rest of the "very interesting - more on that later" photos in the scrap book the race was probably in NY.

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A 6 Day Race historian friend of mine immediately identified it as a "Portable Olympic Track" so it could be anywhere.  Rules out Madison Square Garden as was my first suspicion.  If was fun to find such great 6 Day Race photo's it what is otherwise a pretty common family scrap book.  Enjoy.