Interstate 84 in Oregon

Interstate 84 (I-84) in the U.S. state of Oregon is a major Interstate Highway that traverses the state from west to east. It is concurrent with U.S. Route 30 (US 30) for most of its length and runs 376 miles (605 km) from an interchange with I-5 in Portland to the Idaho state line near Ontario. The highway roughly follows the Columbia River and historic Oregon Trail in northeastern Oregon, and is designated as part of Columbia River Highway No. 2 and all of the Old Oregon Trail Highway No. 6; the entire length is also designated as the Vietnam Veterans Memorial Highway. I-84 intersects several of the state's main north–south roads, including US 97, US 197, I-82, and US 395.

The freeway serves as the main east–west route through Portland and Gresham and continues into the Columbia River Gorge National Scenic Area. It passes through the cities of Hood River and The Dalles within the gorge and also serves several state parks and natural monuments. Near Pendleton, it leaves the Columbia River and runs southeasterly across the Blue Mountains via La Grande and Baker City. I-84 crosses the Snake River at Ontario, continuing southeast towards Boise, Idaho.

I-84 was established in 1957 and originally carried the designation of Interstate 80N (I-80N) until 1980, when this was changed to I-84 to prevent confusion with the southerly I-80. The earliest sections of the freeway incorporated the existing Banfield Freeway between Portland and Troutdale, opened in 1955, and upgraded other parts of US 30 to Interstate standards. New roads were built through the Columbia River Gorge in the 1960s and across northeastern Oregon in the 1970s. The final section of I-84, near Baker City, was opened to traffic on July 3, 1975.

Interstate 84 is the longest freeway in Oregon, at over 375 miles (604 km) in length, and is the only Interstate to traverse the state from west to east. The highway connects the Portland metropolitan area to the Columbia River Gorge, the northeastern Columbia Plateau, and part of the Snake River Valley. As a component of the Interstate Highway System, I-84 is also designated as an important national highway under the National Highway System. It is officially named the Vietnam Veterans Memorial Highway and is mostly concurrent with US 30, which also carries part of the Columbia River Highway No. 2 and all of the Old Oregon Trail Highway No. 6 under Oregon's named route system.

I-84 is maintained by the Oregon Department of Transportation (ODOT), who conduct an annual survey of traffic volume that is expressed in terms of annual average daily traffic (AADT), a measure of traffic volume for any average day of the year. The highway is the busiest in Oregon, with a daily average of over 177,000 vehicles in eastern Portland; while the least-traveled section of I-84, south of Baker City, only carries 9,400 vehicles. The highway's route through the Columbia River Gorge is considered one of the most scenic sections of the Interstate Highway System and is visited by 4.5 million tourists annually.

Interstate 84 begins across from downtown Portland at an interchange with I-5 on the east bank of the Willamette River, between the Burnside and Steel bridges and adjacent to the Oregon Convention Center complex. The interchange is also the terminus of the Banfield Freeway, officially the T.H. Banfield Expressway, which carries I-84 and US 30 through eastern Portland along a railroad grade. The freeway travels northeast through Sullivan's Gulch, passing under the twin overpasses of Oregon Route 99E (OR 99E), which also carries the Portland Streetcar's Loop lines that serve the Eastside district of the city. At an interchange near the Lloyd Center and Holladay Park, the Banfield Freeway is joined by MAX Light Rail trains, which stop along stations on the north side of the freeway.

I-84 serves several local interchanges, which often lack exits for both directions of the freeway, in the neighborhoods of Kerns, Hollywood, North Tabor, and Madison South while following the meandering gulch. After an interchange with OR 213, the freeway intersects the city's north–south bypass, I-205. The two freeways run parallel to each other for one mile (2 km), with I-205 and the MAX Light Rail tracks to the west, the railroad and a multi-use path in the center, and I-84 on the east, along the east side of Rocky Butte. At Fremont Street, I-84 splits from I-205 and the MAX Light Rail tracks to continue east along Sandy Boulevard (US 30 Bypass) through the city's easternmost suburban neighborhoods. The freeway briefly enters northern Gresham and passes through the neighboring cities of Fairview and Wood Village before reaching Troutdale. It passes north of downtown Troutdale and crosses over the Sandy River near Troutdale Airport, entering the Sandy River Delta nature reserve.

I-84 and US 30 emerge from the park at the south bank of the Columbia River, which it follows into the Columbia Gorge National Scenic Area. The freeway runs east along the foot of the gorge, passing through several state parks and scenic viewpoints connected via the Historic Columbia River Highway, including Multnomah Falls—the second-tallest year-round waterfall in the United States and one of the state's most visited tourist destinations. I-84 runs opposite from Washington State Route 14 (WA 14) on the north bank of the river, which also carries Amtrak's Empire Builder passenger trains, and several large mountains that are visible from the freeway. The highway reaches the Bonneville Dam, where it provides the main access to the visitors center on Bradford Island, and passes three regional fish hatcheries. Adjacent to the dam, the freeway reaches a basalt cliff under Tooth Rock, which it traverses using a tunnel for the eastbound lanes and a viaduct for the westbound lanes that overhangs the river. Further upriver from the dam in Hood River County, I-84 intersects the Bridge of the Gods, a toll bridge near Cascade Locks and the first public crossing of the Columbia River east of the Portland area. The bridge also carries the Pacific Crest Trail, a transcontinental hiking trail that follows the crest of the Cascade and Sierra Nevada mountain ranges.