The Kofa National Wildlife Refuge is the large 665,400 acre refuge northeast of Yuma, Arizona. There are lots of interesting backroad trips possible and when hiking you are very likely to see desert bighorn sheep for the refuge is home to about 1000 of them. No permits are needed to visit. The area map is an 8.5 by 11 document in jpeg or pdf format. Kofa Map (jpeg version). Kofa Map (pdf version)

Historical article from Desert Magazine:

February 1942, "Up the West Face of Kofa Mountain" by Ruth Dyer Mendenhall.