Rugged and wide open, with mountains and rangeland, high desert and pine forests, fruit orchards and wheat ranches, eastern Oregon lends its own character to the people who live there. The total population of the 18 Oregon counties and one Washington county that compose the diocese is about 552,000. There are more than 2,600 Episcopalians in the diocese's 22 parishes. Diocesan headquarters are in The Dalles, adjacent to historic St. Paul's Chapel. The other major diocesan property, Ascension School Camp and Conference Center, is in Cove.

Created as a missionary district in 1907, EDEO became a diocese in 1970. But the Episcopal presence in eastern Oregon dates to the late 1800s. One circuit riding priest, the Rev. Reuben D. Nevius, especially left his mark. Nevius, also a botanist, worked in eastern Oregon from 1873 to 1879. He designed and built churches, small architectural gems that still serve congregations. Among them: Ascension Chapel; St. Stephen's, Baker City; St. James, Milton-Freewater; St. Thomas, Canyon City, and the Diocesan Chapel in The Dalles.