Burnside Street originally was named B Street as part of the "Alphabet District" in northwest Portland that was laid out by Captain Couch. B Street extended from the waterfront to 16th Avenue, where it joined Washington Street to continue westward. What we call Burnside Street west of 16th today was considered an extension of Washington, not B Street. This combination of B and Washington Streets formed the principal east-west thoroughfare from the river and led to Tuality Road, a rough road winding through present-day Washington Park over the west hills to the Tualatin Plains.
From milepost 0.0 (at Broadway and Washington) a traveler continued three blocks eastward to 4th Avenue, took 4th north to Burnside and turned east on Burnside to 39th Avenue, then turned south to Stark Street. According to Drinkhall's notes, Stark Street (Baseline Road) was the route to reach the Columbia River Highway.
The highway followed 19th to Burnside, thence east on Burnside to S.W. Washington Street, which took the traveler to milepost 0.0 at S.W. Broadway.
From here, Highway 30 followed Washington to 4th, 4th to Burnside, thence east on Burnside.
Burnside Street History
https://www.portlandoregon.gov/transportation/article/295412
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