In the beginning, the Diocese spanned a vast area, extending from Philadelphia to Pittsburgh. Essentially, it encompassed the whole of Pennsylvania. But the rigors of travel and the growth of the church necessitated reorganization. In 1865, a new Episcopal Diocese of Pittsburgh took responsibility for every parish west of the Alleghenies. By 1910 there were five Episcopal dioceses in Pennsylvania, and the Diocese of Pennsylvania covered only the southeastern corner of the commonwealth. But the bulk of Pennsylvania's Episcopalians lived there - in Philadelphia, Bucks, Montgomery, Chester, and Delaware counties.