Multnomah County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the county's population was 815,428. Multnomah County is part of the Portland–Vancouver–Hillsboro, OR–WA metropolitan statistical area. Though smallest in area, Multnomah County is the state's most populous county. Its county seat, Portland, is the state's largest city.
Image: Portland panorama 3
Image: Mt. Hood (Multnomah County, Oregon scenic images) (mul DA0006)
Image: Portland, OR — St. John's Bridge, view of east tower from southwest
The Boring Lava Field is a Plio-Pleistocene volcanic field with cinder cones, small shield volcanoes, and lava flows in the northern Willamette Valley of the U.S. state of Oregon and adjacent southwest Washington. The field got its name from the town of Boring, Oregon, located 12 miles (20 km) southeast of downtown Portland. Boring lies southeast of the densest cluster of lava vents. The zone became volcanically active about 2.7 million years ago, with long periods of eruptive activity interspersed with quiescence. Its last eruptions took place about 57,000 years ago at the Beacon Rock cinder cone volcano; the individual volcanic vents of the field are considered extinct, but the field itself is not.
Mount Sylvania in Portland, Oregon, one of the major volcanoes in the field
A hiker atop Larch Mountain, the highest elevation in the field
Old-growth forest at Larch Mountain
A core sample showing Portland's geological history, which includes Boring Lava Field deposits, is exhibited on the Washington Park station platform.