Founded in 1798, the Marine Hospital Service originally provided health care for sick and disabled American seaman.

By the late nineteenth century, the growth of trade, travel and immigration networks had led the Service to expand its mission to include protecting the health of all Americans. To reflect this change, the Marine Hospital Service was renamed the Public Health and Marine Hospital Service in 1902.

Ten years later, in 1912, the name was shortened to the Public Health Service (PHS).Under this new name, the PHS was given clear legislative authority “to investigate the diseases of man and [the] conditions influencing the propagation and spread” of these diseases. All types of illness, regardless of their cause, now fell under the control of the PHS.

Throughout the late nineteenth and early twentieth centuries, the Public Health Service was dominated by the Commissioned Corps, a mobile cadre of uniformed and ranked medical professionals.

Many physicians were eager to join the Public Health Service because it offered job stability and a regular paycheck. To ensure that the PHS attracted the nation’s best physicians, applicants to the Commissioned Corps were required to take an exam and to provide detailed information about their medical training.

Although commissions in the PHS were originally limited to physicians, the early twentieth century witnessed a gradual expansion of the Commissioned Corps as scientists joined their ranks.

Throughout this period, commissioned officers were white males. Women and minorities could, however, work in the PHS as civil servants and many did so—as physicians, nurses, biologists, pharmacists and sanitary engineers.

Throughout much of the late nineteenth and early twentieth centuries, the number of commissioned officers was kept fairly low. In 1918, for example, the Public Health Service had fewer than 700 commissioned officers. Charged with the daunting task of protecting the health of some 106 million Americans, PHS officers were stationed in hospitals and clinics not only across the United States but also abroad.

Because few diseases could be cured, the prevention of disease was central to the PHS mission. PHS officers at Ellis Island and elsewhere advocated the use of scientific research, domestic and foreign quarantine, marine hospitals and statistics to accomplish this mission.

The Public Health Service was extremely concerned about the importation of disease into the United States. To prevent this from occurring, the PHS could, and did, impose quarantines on ships which were suspected of carrying diseased passengers and crew. All travelers and immigrants to the United States were also required to undergo a medical exam when entering the country. In 1918 alone, 700,000 immigrants underwent a medical exam at the hands of PHS officers.

Beginning in the late nineteenth century, most PHS officers understood how diseases spread. But without antibiotics, PHS officers were limited in their ability to fight disease.

Quarantine was still the most effective tool for controlling epidemics, but quarantines were difficult to enforce. Additionally, quarantines were often imposed only after an epidemic had emerged.

Interpreters provided an important bridge for patients, the majority of whom did not speak English. Some interpreters spoke several languages and their appearance on the hospital wards provided immigrants with a glimpse into the multi-ethnic character of American society. Reflecting his own multi-ethnic mix as the son of a Jewish mother and an Italian father, Fiorello LaGuardia, one of the island's most famous interpreters, spoke both Italian and Yiddish.

Some Commissioned Corps officers were also conversant in a foreign language. These officers could and did communicate directly with immigrants; however, most PHS officers relied on interpreters. 

Immigrants arriving at Ellis Island and other immigration stations spoke a dazzling range of dialects. Because few interpreters were familiar with these dialects, many immigrants found it difficult to communicate with the staff.

The inability to communicate effectively often caused problems. Looking back at his time at Ellis Island, one officer remembered that "some of the psychiatrists at times weren’t sure whether the interpreter was as familiar as he might be with the dialect of a child." Under these circumstances, deciding whether to deport a patient or allow him to be admitted to the United States could be difficult, if not impossible.