World Trade Center 1 is under construction between SW 1st and 2nd Avenues, Salmon and Taylor Streets. WTC3 is a little further along in its construction at far right and land is cleared to begin WTC2 beyond that. Under the billboard in the foreground sat the Old Main Tavern. It suffered a fire in October 1977 and the whole block would be demolished to be replaced by One Main Place.
Apparently the Old Main Tavern was quite a legendary watering hole. From The Oregonian, July 22, 1977, “…according to Old Main Tavern manager Mike Booth, a ghost which haunts the upstairs of the historic watering hole will have to float elsewhere after the 99-year-old building is razed. His establishment has been a tavern since 1927, he said, but at one time was a house of ill repute. According to legend, a woman was murdered there and her ghost still seeks the killer, opening locked doors and flinging pots and pans through the air.”
(City of Portland Archives)
Vintage Portland 
Sort of depressing that we were advertising cars that got 39 mpg 37 years ago. Now you have to have a Prius to get that kind of gas mileage.
In an earlier Vintage Portland blog post, The building behind the billboard just around the corner was featured as a Mystery Location. The post is here:
In the next to the last comment (by yours truly) is a link to a color photo (courtesy U of O digital collections) of the Old Main Tavern. Dan also found some other photos of the same area and linked to them in the last comment.
I can’t tell from that photo but if that sign was advertising a Datsun B210 those things may have got 39MPG but man those were bad cars.