He is best known for his novella, Interlinear to Cabeza de Vaca (1936), a fictionalized account of the true story of a Spanish conquistador in 16th century North America.
Born to Methodist missionaries Samuel P. and May Clark in what is now Myanmar (then known as Rangoon, Burma), Haniel Long was taken to Pittsburgh at the age of three with his family.
Long moved to Santa Fe, New Mexico in 1929 with his wife Alice and his son Anton for health reasons, and spent the rest of his life there.
In 1936 Interlinear to Cabeza de Vaca appeared, considered Long's best statement of his beliefs on man's place in the world.
Long continued to publish other works over the next two decades: Walt Whitman and the Springs of Courage (1938), Malinche (Dona Marina) (1939), Pinon Country (1941), Children, Students and a Few Adults (1942), French Soldier Home from Being a War Prisoner (1942), The Grist Mill (1945), and A Letter to St. Augustine (1950).