Esther Pohl was a familiar sight around Portland, Oregon, by the summer of 1907. Thirty-five years old, with wavy hair piled atop her head, she was known for bicycling from house to house visiting the patients of her private obstetrics practice. One of the first women in Oregon to practice medicine, she had also served on the city health board since 1905. But on July 11, 1907, she added a new feather to her cap when the health board unanimously elected her Portland’s health commissioner. That made her the first woman to serve as health officer in a major American city.

Pohl began her term battling common infectious diseases of the early 20th century—maladies like smallpox, whooping cough, and tuberculosis, which she called “the greatest evil of this day.” The Oregon Journal called her “one of the best known woman physicians on the coast” as well as “one of the busiest women in the community.”

But before the summer of 1907 was through, she’d confront an even more formidable foe: the bubonic plague. Armed with the latest scientific knowledge and determined not to repeat the mistakes of other cities on the Pacific, Pohl marshalled a response that focused on the real enemy driving the plague’s spread: rats—and their fleas.

Most famous as a medieval scourge that killed millions across Asia, Europe and Africa in the mid-14th century, the bubonic plague was never fully eradicated from the globe (in fact, it’s still around). The 1907 outbreak that threatened Portland—a city that would grow to over 200,000 people by 1910, making it the fourth-largest metropolis on the West Coast—can be traced back to a wave that began in China in the 19th century and then spread along shipping routes. The disease first made landfall on U.S. territory in Hawaii as the century turned. In Honolulu, several Chinese immigrants died of the plague in 1899. Reaction from local officials was swift: All 10,000 residents of the city’s Chinatown were placed under quarantine in an eight-block area surrounded by armed guards. When the disease spread to a white teenager outside the quarantine zone, officials began burning buildings in a desperate attempt to quell the disease. The next January, a stray spark ignited an 18-day blaze that burned down the city’s entire Chinatown. The devastation was brutal, but it also stopped the plague—at least in Honolulu.

In March 1900, the proprietor of a lumber yard named Chick Gin died in a flophouse basement in San Francisco’s Chinatown. Health examiners called to his emaciated body immediately suspected the plague after noticing that his corpse showed swelling in the groin area—a tell-tale sign of the disease (“bubonic” comes from the Greek for groin, boubon). The authorities didn’t even wait until the results were back from the lab to impose a quarantine on Chinatown, trapping about 25,000 people in a 15-block area surrounded by rope. No food was allowed in, and no humans let out.

Well-off white San Franciscans were enraged at the disturbance in their daily lives, since much of the city depended on Chinese workers to cook and clean. Yet many comforted themselves with the idea that they weren’t likely to contract the disease themselves. At the time, the plague was often racialized, as though something in the bodies of immigrant communities—particularly Asian communities—made them more susceptible. It was thought that the plague could only thrive in warm locales, and among those who ate rice instead of meat, since their bodies supposedly lacked sufficient protein to fend off the disease.

City and state officials did their best to stage a cover-up in San Francisco, denying the plague’s presence. As historian of medicine Tilli Tansey writes for Nature, “California governor Henry Gage—mindful of his state’s annual $25-million fruit harvest and concerned other states would suspect a problem—disparaged ‘the plague fake’ in a letter to U.S. secretary of state John Hay and issued threats to anyone publishing on it.” It took an independent scientific inquiry and finally a concerted disinfection campaign before San Francisco was considered safe again in 1904. Meanwhile, 122 people had died.

But the plague wasn’t truly gone from San Francisco—far from it. On May 27, 1907, the city recorded another plague death. This time, however, two key things were different. For one, experts finally had a handle on how the disease was spread: in the guts of fleas carried on rats and other rodents. Although the bacteria that causes the bubonic plague, Yersinia pestis, had been identified back in 1894, at that point scientists were still unclear on how it was spread. At the turn of the century, many believed the bubonic plague was airborne and easily spread from human to human. (Pneumonic plague is spread by droplets, but it’s less common than the bubonic form.) Scientists had long noted that mass die-offs among rats coincided with outbreaks of the plague among humans, but the transmission route wasn’t clear. In 1898, Paul-Louis Simond, a French researcher sent by the Pasteur Institute to the South Asian city of Karachi, demonstrated that infected rat fleas could transmit the plague bacteria, but it took several years and confirmation from other researchers before the idea was well-accepted.

“For most of human history, no city had a chance against plague, because they thought its cause was miasma, or sin, or foreigners,” writes Merilee Karr, who covered Pohl’s efforts against the plague for Portland Monthly. “The realization dawned that rats were involved sometime in the eighteenth or nineteenth century. Acting on partial knowledge was dangerous, because just killing rats would have sent fleas hopping off dead rats to look for new hosts.”

Another thing that was different by 1907: Because public officials now understood how the disease was spread, they were willing to work together to prevent its transmission. The plague was no longer considered a problem that could be confined to a single location: As a port on the Pacific, Portland was vulnerable to the same flea-infested rats scurrying through the harbor and alleys of San Francisco, not to mention Honolulu or Hong Kong. Although San Francisco lagged once again in mounting an effective response, by August 1907, U.S. public health officials were urging anti-plague measures up and down the West Coast, including an order for all vessels in the region to be fumigated and all rats in the ports exterminated.

Esther Pohl went even further. She designed an anti-plague strategy that combined her scientific and technical expertise with an understanding of the power of the press. One of her first big moves, according to Kimberly Jensen—author of Oregon's Doctor to the World: Esther Pohl Lovejoy and a Life in Activism—was to invite reporters and photographers along on her inspection of waterfront. On September 1, 1907, the Oregon Journal published a Sunday exposé headlined “Menace to City’s Health,” describing a horrified Pohl discovering piles of rotting garbage, raw sewage, and a host of “unlovely smells” along the docks. One particular eyesore at the foot of Jefferson Street was used “as a dumping ground and boneyard for all the dilapidated push carts and peddler’s wagons confiscated by police. For half a block there is a wild tangle of milk carts … old rusty iron stoves … worn-out wire cables and rotten wood piles.” The acres of jumbled, broken trash were a perfect breeding ground for rats, not to mention other health issues.

A few days later, Pohl reported on the “indescribably filthy” conditions she found to the city’s board of health, calling for property owners—and the city—to be compelled to clean up their messes. The board was supportive, and on September 11, she made a presentation to the city council. She reminded leaders of a spinal meningitis outbreak just a few months before earlier and warned, “Now we are threatened with a much more dreadful disease.” The measures she recommended were multi-pronged: Garbage had to be properly covered; food had to be protected; and rat catchers had to be hired. Pohl asked for $1,000 to fund the work, with the possibility more would be needed. The city council approved her request—and let her know that if she needed it, they’d give her five times that amount of money.

“She was a compelling speaker,” says Jensen. “Pohl and women's groups used the media effectively by contacting journalists and photographers to document conditions on the waterfront and other areas to raise public awareness and calls for city action. And business owners were particularly concerned about their bottom line and so the council, aligned with business, voted [for] the money.”

Pohl also resisted calls to racialize the plague, even while other local medical experts persisted in drawing a connection between ethnicity and the disease. In December 1907, Oregon state bacteriologist Ralph Matson told the Journal, “If we cannot compel the Hindu, Chinamen and others to live up to our ideals of cleanliness, and if they persist in congregating in hovels and hoarding together like animals ... the strictest kind of exclusion would not be too severe a remedy.” The paper played up his quotes, describing West Coast Chinatowns as “filled with dirt and offal, unsanitary, honeycombed with dark cellars and dark passageways.”

But Pohl never singled out Chinatown, or any other residential community. Portland’s Chinatown, which began to take root in the 1850s, was already under stress thanks to federal exclusion acts and racist violence, with numbers declining from a peak of about 10,000 people in 1900 to somewhere around 7,000 in 1910. Pohl avoided racist rhetoric and targeted the waterfront instead, urging every member of the city’s populace to be vigilant.

In mid-September, Pohl met with Portland business leaders, emphasizing the importance of a clean and vermin-free waterfront. They agreed and formed a committee to go and compel business owners to clean up. C.W. Hodson, the president of the local commerce club, explained to the Journal, “There isn’t any plague here now and we are hoping that there isn’t going to be any—but there must be something done besides hoping.” According to the Journal, most of the merchants on the waterfront were willing to comply with the club’s orders, having already read about the dangerous conditions in the paper.

By mid-September, Pohl also called in outside help: a rat catcher named Aaron Zaik, who had trained in the Black Sea port of Odessa and also worked in New York City and Seattle. The Oregonian emphasized his use of modern methods and chemicals, as well as his mastery over “the psychology and habits of the rodent tribe.” Pohl made him a special deputy on the health board, and was so pleased with his work that after a few weeks she offered his services for free to any property holder.

By the end of October, Pohl added a new prong to the city’s rat crusade: a bounty. She offered Portlanders five cents per rat, brought dead or alive to the city crematory, and instructed them in careful handling so the fleas would be killed alongside the rats. Pohl emphasized that killing rats was a civic duty, telling the Oregonian that “everyone in the city, rich and poor, should consider it his duty to exterminate rats.”

By December, Jensen writes, “the plague scare was essentially over, and Portland

had had no reported cases of the disease.” The co-operation among business, the city council and Pohl was remarkable for a number of reasons, not least the fact that many of the orders had been handed down by a 35-year-old woman at a time when Oregon women didn’t even have the rights to vote. And while multiple reasons factored in, Jensen says that Pohl’s work was key: “Her leadership and her skilled use of publicity made her a touchstone for many people to take action.”

In the end, Portland was the only West Coast port city that didn’t have any plague cases in 1907. Karr says via e-mail, “There has still never been a case of bubonic plague within 100 miles of Portland.” She credits the city’s activated population, “Esther Pohl’s leadership, and Portland’s willingness to follow her to save their city and their own lives.”