A FEW YEARS AGO, on my way from eastern Oregon to Salt Lake City, I pulled off I-84 in Boise, Idaho, a place I knew only from a Lynyrd Skynyrd lyric. I strolled downtown and, in a farmers’ market smelling of lemon sage and lavender, found the best artisanal granola bars west of Burlington, Vermont. As I scanned the pale young crowd and noted the vendors’ earnestly precious names (Hoot ’n’ Holler Urban Farm, Blue Feather Bakery), it occurred to me how much the scene resembled a Saturday morning at Smorgasburg, or at Ferry Plaza in San Francisco, or in Boulder, Sante Fe, or Portland, Maine. The vibe was relaxed, prosperous, and gently urban. Around that time, the real-estate blog Estately ranked Boise fifth on its list of best cities…