The Calapooia River is an 80-mile tributary of the Willamette River in the U.S. state of Oregon. The Calapooia flows generally northwest from its source in the Cascade Range near Tidbits Mountain. In its upper reaches, it passes through parts of the Willamette National Forest. Further downstream, it flows through Holley then Crawfordsville and Brownsv…The Calapooia River is an 80-mile tributary of the Willamette River in the U.S. state of Oregon. The Calapooia flows generally northwest from its source in the Cascade Range near Tidbits Mountain. In its upper reaches, it passes through parts of the Willamette National Forest. Further downstream, it flows through Holley then Crawfordsville and Brownsville in the Willamette Valley before joining the Willamette at Albany. The city of Tangent is also near the river on a branch of one of its downstream tributaries, Lake Creek. The confluence of the two rivers is about 120 miles by water from where the Willamette joins the Columbia River