In the summer of 1938, botanists Elzada Clover and Lois Jotter set off to run the Colorado River, accompanied by an ambitious and entrepreneurial expedition leader, a zoologist, and two amateur boatmen. With its churning waters and treacherous boulders, the Colorado was famed as the most dangerous river in the world. Journalists and veteran river runners boldly proclaimed that the motley crew would never make it out alive. But for Clover and Jotter, the expedition held a tantalizing appeal: no one had yet surveyed the plant life of the Grand Canyon, and they were determined to be the first. Through the vibrant letters and diaries of the two women, science journalist Melissa L. Sevigny traces their daring forty-three-day journey down the river, during which they meticulously cataloged the thorny plants that thrived in the Grand Canyon's secret nooks and crannies. Along the way, they chased a runaway boat, ran the river's most fearsome rapids, and turned the harshest critic of female river runners into an ally. Clover and Jotter's plant list, including four new cactus species, would one day become vital for efforts to protect and restore the river ecosystem. Brave the Wild River is a spellbinding adventure of two women who risked their lives to make an unprecedented botanical survey of a defining landscape in the American West.