[10][11] 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 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.

[3][12][13] I-84 serves several local interchanges, which often lack exits for both directions of the freeway,[14] in the neighborhoods of Kerns, Hollywood, North Tabor, and Madison South while following the meandering gulch.

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.

[15][16] 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.

[3][17] The highway reaches the Bonneville Dam, where it provides the main access to the visitors center on Bradford Island,[18] and passes three regional fish hatcheries.

[23][24] From the bridge, I-84 briefly leaves the river's edge and travels around the south side of Cascade Locks, while US 30 splits from the freeway and runs through the town.

Near this area, the Confederated Tribes of Warm Springs proposed to build a large casino and resort, which was rejected by various governments several times and abandoned in 2013.

[3][12] Upon reaching Mosier, US 30 splits from I-84 and travels inland along the Historic Columbia River Highway while I-84 remains near the riverbank, passing through Memaloose State Park.

[3][15] The freeway passes The Dalles Dam and continues northeast around the foot of Signal Hill and Kaser Ridge to Celilo Village, where it intersects OR 206.

OR 19 travels south to Columbia Ridge, a major landfill that serves Portland and Seattle,[32] and the John Day Fossil Beds National Monument.

[12] After reaching Morrow County, the terrain opens into wide rangelands, including the Boardman Naval Weapons Training Facility that the freeway passes to the north.

I-84 continues through the city of Boardman and turns southeast, leaving the river to intersect US 730 and pass under the Umatilla Army Depot,[3] which is planned to be redeveloped into industrial land and a wildlife refuge.

[34] Formerly a 25,000-acre (10,000 ha) poplar tree farm was planted in rows for 6 miles (9.7 km) along I-84 just east of Boardman and was considered a scenic sight and a community fixture.

[35][36][37] At the southeast corner of the Army depot near Hermiston in Umatilla County, I-84 intersects the southern terminus of I-82, a freeway connecting northeastern Oregon to Washington's Tri-Cities, Yakima, and I-90.

After passing the Eastern Oregon Correctional Institution and crossing the river, US 395 splits from I-84 at Southgate, heading south towards John Day.

[3] The freeway travels southeast through a portion of the Umatilla Indian Reservation, passing the on-reservation resort casino,[39] and begins its ascent into the Blue Mountains.

[12] The easternmost 168 miles (270 km) of I-84 includes several sharp curves and steep grades, along with winter weather that causes frequent closures and collisions.

The freeway continues south through the Grande Ronde Valley to Ladd Canyon, which it follows while gently ascending part of Craig Mountain at the edge of the Wallowa-Whitman National Forest.

I-84 and US 30 are rejoined and follow Sutton and Alder creeks southeast through Pleasant Valley, an area notorious for inclement weather due to its microclimate.

At Durkee, the freeway begins to follow the Burnt River, passing Rattlesnake Springs State Park, Weatherby, and Lime.

The freeway leaves the river at an interchange with OR 201 near Huffman Island and continues southeast across several cuts and embankments dug into an arm of the Blue Mountains.

I-84 travels south and passes Ontario's northbound welcome center, which receives up to 55,000 visitors annually,[44] before crossing the Snake River into Idaho west of Fruitland.

6, which followed the historic Oregon Trail from Pendleton to Ontario on the Idaho state border, passing through La Grande and Baker City.

[2][59] After the passing of the Federal Interstate and Defense Highways Act in 1956, US 30 was scheduled to be superseded by a new freeway, on an alignment closer to the river on flat terrain.

Construction on the remaining segment between Pendleton and Ontario began in 1965 and continued until July 3, 1975, when the final section of I-84 opened near Baker City.

[6] In November 2016, ODOT activated a variable speed zone on a 30-mile (48 km) stretch of Interstate 84 between Baker City and Ladd Canyon.

[2][70][71] The full length, stretching 13 miles (21 km) from the Burnside Bridge to Troutdale, opened on January 24, 1958, with the completion of the section west of Northeast 42nd Avenue.

[78] Construction of the widened freeway and light rail line required the demolition and replacement of twelve overpasses and the closure of several ramps.