US 99 then continued north along present I-5 into Washington; the next segment still numbered 99 is WA 99 south of Seattle.

It heads west through downtown Eugene along OR 99 and OR 126 Business, and then northwest and north to Junction City on OR 99.

It passes through the winemaking towns of Dundee and Newberg before entering the Portland suburb of Sherwood.

OR 99W then skirts the city of Tualatin and passes through Tigard before entering Portland and immediately ending at I-5.

South of the Ross Island Bridge approach, Oregon Highway 99W and OR 10 split from Barbur Boulevard onto Naito Parkway, an arterial that once connected directly to Harbor Drive.

At the overpass over I-405 is the former split with Harbor Drive, which was replaced by Tom McCall Waterfront Park in 1974.

The Pacific Highway West continues north through downtown, locally maintained along Naito Parkway, to the state-maintained Steel Bridge.

The section north of Portland was initially named Multnomah Boulevard until Interstate Avenue was adopted in 1916; the street was paved in the late 1920s amid several minor realignments to provide for a 100-foot (30 m) wide highway.

The original alignment in southern Portland, bypassed in the 1930s by Barbur Boulevard, is still called Capitol Highway.

Harbor Drive was removed in 1974, resulting in OR 99W moving west one block to Front Street (now Naito Parkway) downtown.