Specializing in performing symphonic works strictly by American composers, the American Composers Orchestra was originally conceived in 1975 by composer Francis Thorne and conductor Dennis Russell Davies. Realizing that the majority of American-based orchestras failed to play works composed by Americans, the duo set out to correct the problem on their own. With Davies serving as the orchestra's principal conductor and music advisor, composer Nicolas Roussakis and conductor/flutist Paul Lustig Dunkel also signed on shortly thereafter, leading to the A.C.O.'s inaugural concert on February 7, 1977, at Alice Tully Hall at Lincoln Center. The orchestra proved to be a success, leading to a permanent home at Carnegie Hall beginning on its tenth anniversary, during the 1985-1986 season (Robert Beaser was named composer-in-residence in 1988 and six years later, became the orchestra's artistic advisor). The A.C.O. has featured countless renowned special guests over the years, including Leonard Slatkin, Michael Tilson Thomas, Leonard Bernstein, Itzhak Perlman, André Watts, and Emanuel Ax, among others.

Since its formation, the American Composers Orchestra has tirelessly stuck to its original mission, programming 500 works by more than 400 American composers and leading to recordings on such labels as Argo, CRI, ECM, Point, Music Masters, Nonesuch, Tzadik, and New World, plus several special awards from the American Academy of Arts and Letters; Broadcast Music, Inc.; and the American Society of Composers, Authors, and Publishers. By the early 21st century, the American Composers Orchestra was led and conducted by both Steven Sloane (also its music director) and Beaser, while its founding conductor, Dennis Russell Davies, became the A.C.O.'s first conductor laureate during the spring of 2002. The American Composers Orchestra also encourages musical education for youngsters, as it formed the Music Factory in 1999, an educational program that unites composers with students from public elementary and high schools. The American Composers Orchestra has also served as a launching pad for such composers as Ellen Taaffe Zwilich and Joseph Schwantner, both of whom were granted their very first orchestral commissions courtesy of the A.C.O. ~ Greg Prato, Rovi