Marathon III, part of Welcome Week, took place at Memorial Stadium at the U of M on September 23, 1973, according to the Insider.  Groups performing were:

• Paul Butterfield’s Better Days
• Freddie King
• David Bromberg
• New Grass Revival
• Michael Johnson
• Ellen McIlwaine
• Moondogg and Muledeer Medicine Show was/were? the emcees.

Johnny Hanson sez:

It was a helluva lineup but it was really a cold day.  By evening it was nearly freezing  Some folks in the bleachers next to us collected trash and built a bonfire (not good).  Bromberg got halfway thru his set and apologized:  “Our fingers are freezing to the strings” and that was that.

Image courtesy of the Insider