In 1943, Barber and Menotti purchased ‘Capricorn’, a house north of Manhattan in suburban Mount Kisco, New York. The home served as their artistic retreat up until 1972, and it was at this house that Barber had his most productive years as a composer during the 1940s, 1950s, and early 1960s. Here he wrote ballet suite "Medea" (1946) for Martha Graham and the symphonic work "" for soprano and orchestra for opera singer Eleanor Steber who premiered the work with the BSO in 1948. In 1946 he was selected by the United States State Department to be a member of the American delegation to the first Prague Spring International Music Festival where his music was showcased alongside other prominent American composers such as Leonard Bernstein. In 1949 he achieved a major critical success with his "Piano Sonata" which was premiered by Vladimir Horowitz and commissioned by Irving Berlin and Richard Rodgers to celebrate the 25th anniversary of the League of Composers. Popularized in concerts internationally by Horowitz and other prominent pianists, the work earned an enduring place in the performance canon.