The May 1970 student strike at the University of Washington was part of a national week of student strikes, organized in reaction to the expansion of the Vietnam War in Cambodia, the killings of student protesters at Kent State University, and "to reconstitute the University as a center for organizing against the war in Southeast Asia." Student activists called for a strike on May 4, after the events at Kent State, and the next day six thousand students attended a strike rally and then marched off campus, charging onto the freeway, blocking traffic for hours as they marched downtown. For the next two weeks, the strike continued and with it several additional freeway marches and some window smashing demonstrations. The campus, the university district, capitol hill, and parts of downtown Seattle felt the effects of this extraordinary mobilization.
Here is a detailed account by Zoe Altaras, The May 1970 Student Student Strike at the University of Washington.
Here are photos of student protests, including the strike, from the Steve Ludwig Collection
Below are documents of the strike collected by Steve Ludwig. Click for a larger, readable image.