The police and Fire Department crews have responded to trouble in the camp more than 820 times in the last five years, including 70 violent incidents, 500 emergency medical calls and 250 fires. Last year was the worst for violence in a decade. The shootings in January led to the arrests of three teenage brothers, who are homeless themselves and now in jail.

“You step in there, and it’s like you’re not even in the United States anymore,” said Harold Scoggins, the chief of the Seattle Fire Department, who went into the Jungle after the shootings with a group of public health and safety officials for two days of study.

Most big cities have a Jungle by some other name — a stretch of woods by the railroad tracks, an industrial property gone to seed, a skid row. And in other big cities with major homeless populations, like Los Angeles, San Francisco and New York, the problem is also front and center on the streets. In San Francisco, for example, after warning the homeless in a particular encampment that they would have to leave by Friday for public health reasons, officials on Tuesday began clearing out the belongings of the few dozen people who had refused to go.

But Seattle, where Mayor Edward B. Murray declared a state of emergency over homelessness in November, is being looked to as a model by some other cities because of its strategy of setting aside areas for authorized tent camps that are overseen by social service agencies and governed by rules of conduct. On Friday, for example, city councilors from Sacramento paid an official visit to Seattle’s designated tent cities to weigh adopting the strategy back home.