The World Trade Organization Ministerial Conference of 1999 was scheduled to take place in Seattle on November 30. The low-ball estimate is that a record 40,000 anti-globalization activists showed up to protest the meeting, and shut it down entirely if possible.
Activists blocked traffic at major intersections, thereby preventing delegates from getting to the conference, and police responded by firing tear gas, pepper spray and, eventually, rubber bullets, to disperse the crowds and get delegates through.
Protesters responded by destroying storefronts, pushing flaming dumpsters into intersections and slashing the tires of police cars. Utimately, 600 people were arrested, chief of police Norm Stamper stepped down and the vandalism caused $20 million in damages.