Born in Detroit, Michigan,[1] Friel, a 1909 Yale University graduate, had been South American editor for the Associated Press which led him into his subject matter.
Friel began appearing in Adventure magazine in 1919 with stories set in the Amazon jungle featuring the characters Pedro Andrada and Lourenço Moraes, two seringueiros (rubber-industry workers) who undergo harrowing experiences in the impenetrable jungle surrounding the Javary River, an Amazon tributary which forms part of the border between Brazil and Peru.
Some of the Pedro and Laurenco stories feature minor science fiction elements, such as lost civilizations and ape-human hybrids.
The first ones, featuring a trio of adventurers called McKay, Ryan and Knowlton, and other characters, were The Pathless Trail, Tiger River, The King of No-Man's Land and Mountains of Mystery.
An unabridged audiobook of Amazon Nights: Classic Adventure Tales from the Pulps read by Tony Scheinman was released in 2012.