As authorities prepared to evict its residents, a reporter spent six weeks in Dallas’ biggest homeless camp.

The murders were the catalyst. Now the authorities had to do something. On February 17, a Dallas Morning News headline declared that “Dallas officials want Tent City shut down after 2nd killing in a month.” In early March, the City Council approved a plan to empty the homeless encampment, a five-block stretch beneath I-45 at the point where it meets I-30, about a mile south of downtown.

“This is no way for any human to live,” Mayor Mike Rawlings declared. “I don’t care if someone says, ‘I want to live underneath this bridge.’ That’s just not acceptable in Dallas, Texas.”

Many of the mayor’s liberal fans were puzzled by the ultimatum. Rawlings had formerly held a volunteer position as the city’s “homeless czar” and was widely credited as the force behind the erection of The Bridge, an extensive donor- and tax-supported shelter that bills itself as the area’s “homeless recovery center.”

The idea of leveling the encampment didn’t square with administrative objectives, either. Last fall, the camp’s population boomed from about 60 to about 300. A dozen Tent City residents told me the police urged them to move there, and in a way that made sense: The area had long been home to several shelters and soup kitchens. It was as if bureaucrats and cops wanted to centralize the problem of people living on the streets.

Activists with the Metro Dallas Homeless Alliance (MDHA), an umbrella of some six dozen aid organizations, persuaded the council to place dumpsters and portable toilets on each of Tent City’s blocks. The encampment quickly became a hub, ....