A Southern man of letters, Percy befriended many fellow writers, Southern, Northern and European, including William Faulkner. He socialized with Langston Hughes and other people in and about the Harlem Renaissance. Will was a sort of godfather to the Fugitives, or Southern Agrarians, as John Crowe Ransom, Allen Tate and Robert Penn Warren were often called, at Vanderbilt.
Percy's family was plagued with suicides, including his first cousin LeRoy Pratt Percy. William adopted his cousin's children, Walker Percy and two siblings, LeRoy and Phin after their parents' death. LeRoy went on to marry Sarah Farish, the exquisite daughter of Will Percy's law partner, Hazelwood Farish and took charge of the Percy family plantation, Trail Lake. Phin married and moved to New Orleans to practice law.
Percy's most well known work is his memoir, Lanterns on the Levee: Recollections of a Planter's Son (Alfred A. Knopf, New York 1941). His other works include the text of "They Cast Their Nets in Galilee," which is included in the Episcopal Hymnal 1982 (Hymn 661), and the Collected Poems (Knopf 1943). One piece by Percy is included under the name A.W. Percy in Men and Boys, an anonymous anthology of Uranian poetry (New York, 1934).
A friend of Herbert Hoover from the Belgium Relief Effort during the early years of World War I, he was put in charge of relief during the great flood of 1927, when an area larger than all New England (minus Maine) was inundated. During the flood, thousands of African-Americans fleeing inundated farms and plantations sought refuge on the levee in Greenville. Percy believed that they needed to be evacuated to Vicksburg, Mississippi and ships were prepared to remove them. However, local planters, including Percy's own father, opposed this decision, believing that if the African-Americans were removed from the area, they would never return. Percy capitulated and the ships left Greenville empty. Thereafter, conditions on the levee deteriorated and Percy received his share of negative press. He later resigned his post and left for a trip to Japan the following day.
The William Alexander Percy Library in Greenville, Mississippi is named for him.