As of 2012, Portland was the largest city in the United States that did not add fluoride to its public water supply, and fluoridation has historically been a subject of controversy in the city. Portland voters have four times voted against fluoridation, in 1956, 1962, 1980 (repealing a 1978 vote in favor), and 2013. In 2012 the city council, responding to advocacy from public health organizations and others, voted unanimously to begin fluoridation by 2014. Fluoridation opponents forced a public vote on the issue, and on May 21, 2013, city voters again rejected fluoridation.