As he navigated one day last fall through a crowded grid of beds at one of Oregon’s largest homeless shelters, Steve Martin, a longtime rancher and community volunteer, was brought to a halt by a familiar voice that called out from an unfamiliar face.

“Aren’t you going to say, ‘Hi,’ Steve?” said the man, with eyes peering through curtains of white hair and a beard that flared in neglected disarray. Mr. Martin, who spent many of his days working among the shelter’s residents, considered the man’s gaunt frame, searching for a clue. Then the man spoke again: “It’s Craig.”

The words jolted Mr. Martin with a mix of recognition and disbelief. He had known Craig Coyner for more than 50 years, watching with admiration as the man from one of the most prominent families in Bend, Ore., rose through an acclaimed career — as a prosecutor, a defense lawyer and then a mayor who helped turn the town into one of the nation’s fastest-growing cities.

Now, at age 75, Mr. Coyner was occupying a bed at the shelter on Second Street, his house lost to foreclosure, his toes gnarled by frostbite, his belongings limited to a tub of tattered clothing and books on the floor next to his bed.

In the years since the two old friends had fallen out of touch, Mr. Coyner had been pulled through a vortex of the same crises that were churning through many boom towns across the West: untreated mental illness, widespread addiction, soaring housing costs and a waning sense of community. After a life spent as a pillar of Bend’s civic life, Mr. Coyner had somehow reached a point of near total destitution, surrounded by the prosperity he had helped create.

Once a tiny timber town, Bend had undergone a striking transformation in recent decades, as moneyed newcomers from Seattle or Portland or San Francisco discovered a getaway that managed to be both trendy and a throwback to what everyone imagines small-town America can be. Families could float the Deschutes River in the summer and ski the Cascades in the winter, stopping at an array of craft breweries, organic eateries, art galleries and — a point of special pride for the city — the last Blockbuster video store on Earth.

But as housing costs strained the budgets of Bend’s nurses, teachers and police officers, homelessness soared in the city of 100,000 people, much as it had in far larger West Coast cities. RVs started parking on side streets; people with full-time jobs at gas stations and grocery stores at times went home to tents erected in the sagebrush along street medians. The shelter where Mr. Coyner had finally found refuge had been over capacity for months.

Mr. Martin’s mind raced with questions for Mr. Coyner, as he wondered what had transpired in the years since they last connected and how Mr. Coyner’s life could have taken such a drastic turn.