From Dunmore, Co. Galway, Ireland, Dr. Gannon became a physcian, married and then emigrated with his family to take a position in St. Louis, Missouri in 1967. By playing music on the piano accordion and harmonica, PJ encouraged his family to learn music and to keep the Irish traditions alive. PJ worked in hospitals throughout St. Louis as a physiciatrist for almost 50 years. Now fully retired, he enjoys teaching weekly lessons in singing, recitation and harmonica at St. Louis Irish Arts.
PJ is the winner of two senior Fleadh Cheoil na hÉireann championships on the harmonica. In September 2007, PJ travelled to the Comhaltas cultural center Bru Boru in Cashel, Co. Tipperary, Ireland for the official release of "P.J. Gannon – Harmonica and Harp", featuring slows airs on harmonica accompanied by his daughter Eileen Gannon on harp, as well as recitations by various poets including the famous W. B. Yeats.
Most recently, one of P.J's harmonica 9-year old students took third place in the All-Ireland competitions in Derry, in Northern Ireland.