A public waterworks was created by City Charter Amendment in 1875. However, Seattle was served primarily by small private water companies for the next decade-and-a-half. Following the Great Fire of 1889, citizens voted to fund creation of a municipally owned water system. The City purchased the private systems, and since 1891, has owned and operated a municipal water system. The City began developing the Cedar River Watershed and contracting with outside communities (such as Ballard and Renton) for the sale and provision of water to those communities. The system was administered by the Superintendent of Water under the auspices of the Board of Public Works. In 1905 the Department of Lighting and Water Works was created. Five years later, the Water Department became a separate entity. In 1952, development of the Tolt River as a secondary water source was recommended; this development took place in the 1960s. In 1997 the Water Department was consolidated with the utilities of the Engineering Department to form Seattle Public Utilities.

With tooth decay prevalent among Seattle's children, Dr. Emil Palmquist, Seattle-King County Department of Public Health director, put forth a suggestion to add fluoride to Seattle's drinking water in 1951. Fluoridation was a hotly debated topic in the 1950s and 1960s, with health professionals, organizations, and citizens on both sides of the issue.

A variety of groups and individuals -- citizens as well as health professionals -- opposed fluoridation. Many felt that fluoridation was "compulsory medication" and violated an individual's right to choose what treatments and medication to seek out for him- or herself; these opponents made the case that fluoridated milk, juice, or even vitamins could be made available to those families that chose to purchase these items. Religious concerns affected the issue as well, as many religions oppose the use of certain forms of medication or treatment. For example, although the Church of Christ, Scientist supported the rights of individual families to use fluoride supplements, it was one of the most vocal groups in opposition of fluoridated drinking water. Furthermore, opponents argued that the dosage was not adjusted for individual needs, and cited a variety of potential harmful effects, including mottling of teeth and risks of more serious diseases, such as cancer. A few went so far as to suggest that fluoride in the water set a "precedent for compulsory mass dosing for other purposes."

On the other hand, fluoride's advocates argued that not fluoridating Seattle's water infringed upon the rights of all children to have proper tooth care. Low-income families might not have the option of frequent visits to the dentist or of purchasing fluoride-added items, and thus, fluoridated water was the cheapest and most effective way to improve the teeth of all children, regardless of the family's economic status. Advocates maintained that fluoridation of drinking water was a cheap and safe solution to reducing tooth decay. Furthermore, in response to opponents' charges that fluoridation abridged individual rights, a Seattle Times article of February 2, 1963 stated that "[c]ourts have held that fluoridation is a proper function of government and does not infringe on individual rights." The fluoridation recommendation was endorsed by many health professionals and organizations, including the State Board of Health, and by other citizens' organizations such as the Seattle Council of Parent Teacher Associations.

In 1952, a proposal to add fluoride to the water was defeated by almost a two-to-one margin. The proposal was again defeated in 1963, although the vote was comparatively much closer. In 1968, the Seattle City Council voted 5 to 4 in favor of fluoridation. The Council then chose to allow the voters to decide, and -- sixteen years after its initial rejection -- fluoridation was approved, and Seattle joined large cities such as Chicago, Philadelphia, San Francisco, and Washington D.C. in adding fluoride to its drinking water.