William Thompson Sedgwick (December 29, 1855 – January 25, 1921) was a teacher, epidemiologist, bacteriologist, and a key figure in shaping public health in the United States.

His students became the spokesmen and practitioners who brought the principles of public health into the practice of engineering beginning in the 1890s and lasting well into the 20th century.

[3] He instilled in his students the need to develop three basic behaviors: a vision of the subject in relation to the broader world, an honest method of working to seek the truth and an enthusiasm for service to the profession the public.

[5] In 1902, he published the groundbreaking book Principles of Sanitary Science and the Public Health, which was a compilation of his lectures from the courses he taught at MIT and a distillation of his experience working in the field.

[6] Sedgwick’s courses at MIT and his influence on civil engineering students there can be considered the first instructions in the field of public health.

In 1913, he joined with George C. Whipple and Milton J. Rosenau to establish the Harvard-MIT School for Public Health Officers.

He directed bacteriological research at the Lawrence Experiment Station and sent his brightest engineering students to work there—including George W. Fuller and Allen Hazen.

[2] Even though he was not known for his laboratory research studies, he was responsible, along with George W. Rafter in 1889, for developing the enumeration procedure and apparatus for examining microscopic organisms in surface water bodies.

“In the Annual Report of the State Board of Health of Massachusetts for 1892, Sedgwick presented studies on typhoid fever epidemics at Lowell and Lawrence, at Springfield and at Bondsville, which were classics in the field and which make this one of the most outstanding volumes in the history of epidemiology.”[10] At the end of the 19th century, the water supply for Jersey City, New Jersey was contaminated with sewage and the death toll from typhoid fever was high.

In 1899, the city contracted with a private company for the construction of a new water supply on the Rockaway River, which included a dam, reservoir and 23-mile pipeline.

In the first trial, he testified that the water that was supplied to the city was contaminated with bacteria from sewage discharges in the watershed above the reservoir.

[11][12] In the second trial, Sedgwick disagreed strongly with the proposal by John L. Leal to treat the water from the reservoir with calcium hypochlorite, which was called chloride of lime at that time.

He also testified that chlorination did not remove organic matter, particulates and other filth, which could weaken the vital resistance of water consumers.

However, the chlorination system was found to be safe, effective and reliable by the Special Master, William J. Magie, and was judged capable of supplying Jersey City with water that was "pure and wholesome.

He believed that women’s suffrage and feminism "... would mean a degeneration and degradation of human fibre which would turn back the hands of time a thousand years.