 In addition he received the 1946 Pulitzer Prize for Music for his cantata, the "Canticle of the Sun", written in 1944 (; )

In 1927 he became organist-choirmaster at St James’s Episcopal Church, Chicago, which was consecrated as a cathedral while he was there (1955).Previously, Sowerby was associate organist at Fourth Presbyterian Church of Chicago (1919).In 1962, after his retirement from St James’s, he was called to Washington National Cathedral to become the founding director of the College of Church Musicians, a position he held until his death in 1968 .