SAN FRANCISCO — Ira Watkins paints his pictures in a faded Dodge van with velveteen seats parked beside a center for seniors in the Tenderloin, a seamy part of town frequently associated with displaced loners, drug addicts in squalid alleyways and other manifestations of human misery.

Mr. Watkins, a courtly 73-year-old Texan, has spent three years living and working in his van while awaiting permanent housing. He is an accomplished painter with a recent gallery show to his credit, but the trajectory of his life is pure Tenderloin: a past, now distant, in which precious years and untold dollars were lost to a crack habit. “I found something I liked to do better,” he said, rapping on a fresh oil painting taped to a board.

Mr. Watkins is one of more than 200 artists identified as “hidden gems” of the Tenderloin by the Wildflowers Institute, a nonprofit organization that helps communities define their cultural assets. In this case, the goal is to take a small stand against gentrification, casting a positive light on the people most likely to be displaced by the wealthy. Lately, more than a dozen technology companies, including Twitter, have relocated alongside the impoverished neighborhood, some buoyed by city tax breaks. The prospective changes to the Tenderloin — a noirish haunt of Dashiell Hammett’s Sam Spade and arguably the central city’s last working-class neighborhood — have given rise to a new nickname: the Twitterloin.

Once a thriving hub of the city’s night life, from theaters with gilded prosceniums to French restaurants with private bedrooms, the Tenderloin was until recently the place the tech economy forgot. The dense 40-block neighborhood — bordered by City Hall, affluent Nob Hill and Union Square — has been down on its heels since the 1960s, when its 100 or so historic residential hotels, believed to be the largest concentration in the country, began housing those left behind by urban renewal.