Koreatown, LOS ANGELES—Resting inside one of the stone entryways of St. James Episcopal Church on St. Andrews Place, Josh Law heard a drunken man’s slurred speech and then the sound of an opening zipper. In 16 months of homelessness, Law had learned to sleep in an altered state of hypervigilance. He grabbed his makeshift bed of clothes and blankets—and dodged the stream of urine. Sixteen long months of hell, Law says. Sixteen months of adjusting his nightly agenda to the event schedule of the church so that he wouldn’t block a doorway with his bed. Sometimes he stretched out at 8 p.m.; sometimes he waited until 10 p.m. He always made sure he was up at 4 a.m., before the garbage truck drivers passed. “I didn’t want people to see me and think: ‘Oh, what a lazy homeless bum,’ ” Law said. But the number of homeless people in this country is steadily increasing; there are far too many for literal—or figurative—invisibility. The statistics extend gloomily from there. Advocates who work with the homeless estimate there are at least 2 million unhoused people in the United States. Between 2018 and 2019, according to the Los Angeles Homeless Services Authority’s count, the homeless popula...