Use in the public domain: Michael McConnell Files, "America’s First Gay Marriage" (Binder #7), Tretter Collection in GLBT Studies, University of Minnesota Libraries (USA).
An affidavit from Egil Jonsson says, "I was personally present at the civil rights march depicted in the photograph."
Also, the photo "was included in a Gay-rights flyer handed out at a booth hosted by the Minnesota State Fair during August 1973."
Licensing
This photo lost its federal protections [37 C.F.R. 202.2(a)(2)] in 1973 and entered the public domain because of publication via distribution without a notice of copyright.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.