On Oct. 16, 1940, the House of Bishops and the House of Deputies adopted an official flag for the Episcopal Church. This was the 251st anniversary of the day the General Convention ratified the Constitution and Canons and adopted the BCP. It was designed by William M. Baldwin (d. 1942), a member of the Cathedral of the Incarnation, Long Island, New York.
The symbolism of the flag has been explained as follows: The white field represents the purity of the Christian religion. The red cross represents the sacrifice of Jesus and the blood of the martyrs. The red cross on a white field is the cross of Saint George, the patron saint of England, indicating our descent from the Church of England. The blue in the upper left-hand corner is the light blue of the sky, often used by artists for the clothing of the Blessed Virgin. It is called Madonna blue and represents the human nature of our Lord, which he received from his mother. The nine white crosslets on the blue field represent the nine original dioceses of the Episcopal Church in America in 1789: Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Virginia, Delaware, and South Carolina. They are arranged in the form of a St. Andrew's Cross to commemorate the fact that Samuel Seabury, the first American bishop, was consecrated in Aberdeen, Scotland, on Nov. 14, 1784. The colors red, white, and blue represent the United States and stand for the American branch of the Anglican Communion.
The same design is incorporated in the Episcopal Church seal, which was also adopted by the 1940 General Convention. The seal and flag serve as emblems of the Episcopal Church
(from An Episcopal Dictionary of the Church.)
