We have an unknown distance yet to run, an unknown river to explore. What falls there are, we know not; what rocks beset the channel, we know not; what walls ride over the river, we know not. Ah, well! we may conjecture many things.

Before setting out Powell used Hamblin as a negotiator to ensure the safety of his expedition from local Indian groups. Civil war and aftermath
Powell's loyalties remained with the Union and the cause of abolishing slavery. Gathering nine men four boats and food for 10 months he set out from Green River Wyoming on May 24.

Powell served as second director of the US Geological Survey (1881–1894) and proposed policies for development of the arid West which were prescient for his accurate evaluation of conditions. He is famous for the 1869 Powell Geographic Expedition a three-month river trip down the Green and Colorado rivers that included the first known passage through the Grand Canyon.