On May 21, 2002, the Holy Father Pope John Paul II accepted the Chaldean Synod’s election of Fr. Sarhad Jammo and named him the first bishop of the newly-created Diocese of St. Peter the Apostle, which covers the 19 westernmost United States: Alaska, Arizona, California, Colorado, Hawaii, Idaho, Kansas, Montana, Nebraska, Nevada, Oklahoma, New Mexico, North Dakota, Texas, Utah, Washington and Wyoming. The Episcopal Consecration of Bishop Sarhad Yawsip Jammo took place at 4:30 P.M. on July 18, 2002, the eve of the Feast of Mar Mari, the apostle to Mesopotamia, at St. Joseph Catholic Chaldean Church in Troy, Michigan, where Mar Sarhad served as Pastor for almost twenty years. The principal consecrator was His Beatitude Mar Raphael I Bidawid, Patriarch of Babylon of the Chaldeans, of blessed memory.
Among those in attendance were: His Beatitude Mar Dinkha IV, the Patriarch of the Assyrian Church of the East; His Beatitude Mousa Cardinal Daoud, Prefect of the Congregation for the Oriental Churches; His Eminence Adam Cardinal Maida, Archbishop of Detroit, His Excellency Emmanuel Delly, Patriarchal Auxiliary; His Excellency Mar Ibrahim Ibrahim, Bishop of the Eparchy of St. Thomas; and His Excellency Mar Bawai Soro, Bishop of California for the Assyrian Church of the East. Mar Sarhad Yawsip was installed as bishop at St. Peter Chaldean Cathedral in El Cajon, California on July 25, 2002.
On August 29, 2017, after the Retirement of Bishop Sarhad Yawsip, Bishop Emanuel Shaleta was installed as Bishop of the Eparchy.
The Diocese of St. Peter the Apostle is split into three Vicariates: South, North, and East.