High Quality Content by WIKIPEDIA articles! The Roman Catholic Diocese of Davenport is a diocese of the Catholic Church for the southeastern quarter of the state of Iowa. There are 11,438 square miles (29,620 km2) within the diocese. The diocese`s eastern border is at the Mississippi River; the northern border comprises the counties of Jasper, Poweshiek, Iowa, Johnson, Cedar, and Clinton; the western border is made up of the counties of Jasper, Marion, Monroe, and Appanoose; and the southern border is the Iowa-Missouri border.