I came upon this incredible website filled with images of Seattle from the 1970s and into the 80s thanks to mhays at the Seattle regional forum. The photos were taken by Stephen Cysewski in Pikes Place Market, Pioneer Square, the waterfront, First Avenue, etc. and show both some urban grit and the people of its time.
Keep in mind the photos posted here are only a fraction of what can be found on the photographers website below: http://www.cysewski.com/seattleweb/