His best known opera, Susannah, is based on a story from the Biblical Apocrypha, transferred to contemporary rural Tennessee, and written for a Southern dialect.

It was premiered at Florida State at the Ruby Diamond Auditorium[11] in February 1955, with Phyllis Curtin in the title role and Mack Harrell as the Reverend Olin Blitch.

[1] It was selected to be America's official operatic entry at the 1958 World's Fair in Brussels,[1][11] directed by Frank Corsaro, with Curtin, Treigle and Richard Cassilly.

The Passion of Jonathan Wade, commissioned by the Ford Foundation, was Floyd's most epic opera, set in South Carolina during the Reconstruction era.

Theodor Uppman, Curtin, Treigle and Harry Theyard performed in a large cast, conducted by Julius Rudel and directed by Allen Fletcher.

[1] A monodrama on the royal subject of Eleanor of Aquitaine, Flower and Hawk, premiered in Jacksonville, Florida, with Curtin directed by Corsaro.

[18] Bilby's Doll (after Esther Forbes) was commissioned by the Houston Grand Opera where it was premiered in 1976 with Christopher Keene conducting and David Pountney directing.

[1] Floyd composed Willie Stark (after Robert Penn Warren) also for Houston, where it was first heard in 1981 in a staging by Harold Prince.

[1] After a hiatus of almost twenty years, another Floyd opera premiered in Houston in 2000, Cold Sassy Tree (after Olive Ann Burns).

[11] He had composed a Piano Sonata in the 1950s (1957, two years after Susannah) for Rudolf Firkušný, who played it at a Carnegie Hall recital, but it languished until Daniell Revenaugh recorded it in 2009 at the age of 74.

The recording was made on the Alma-Tadema Steinway that graced the White House during the presidencies of Theodore Roosevelt and Woodrow Wilson.

[11] The National Public Radio's Tom Huizenga posits the work as suitable contender to be considered the archetypal "Great American Opera".

[11] The Daily Telegraph, however, claimed it is the most "widely performed" American opera, purportedly outnumbering some works by Mozart, Verdi and Puccini.

[13] In addition to Gershwin and Menotti, Floyd stands with Adams, Barber, Bernstein, Glass and Rorem in the pantheon of preeminent 20th-century American opera composers.