SL4-139-3932 (December 1973) --- A 70mm hand-held Hasselblad photograph showing parts of Minnesota, Iowa and Wisconsin. Lake Superior is in the upper part of the photo; Duluth at upper left; Castle Rock Flowage and Petenwell Flowage at far right center. Note circular feature (partially formed by rivers) which the Skylab 4 crewmen commented on when they made this fly-over. Photo credit: NASA