I'm still working, slowly, on researching the history of whitewater rafting in Idaho. In their book The Middle Fork: A Guide (3rd ed.), Johnny Carrey and Cort Conley write about Ruth Hindman and the year 1946:
That year Ruth Hindman ran her own rubber raft down the Middle Fork -- the first woman to do so. The only problem to arise was a tube that blew out while the raft was ashore. Since patching material could not be located, they tied a knot in the diaphragm and finished the run without further headaches. Ruth repeated her accomplishment a year later. In the late 1940s, she, along with Ruby Taylor and Coralie Thomson, held professional guide's licenses on Oregon's McKenzie River.
The end of World War II meant inexpensive surplus rubber rafts could be purchased by the public. After Amos Burg and Ruth Hindman, others were not long in testing inflatables on the river. (p. 81-82, 84)
Hindman, who was clearly a badass, ran the river in 1946; fifty-one years later, I ran my own raft down it for the first time at age 17. There are lots of stories of male river-running pioneers, but I'm enjoying these little treasures of female pioneers, too; for a long time in my youth, I didn't know or see other women running boats.