Or as Charlie Campbell put it as he pulled a beer, “It is what it is.”

The diminutive establishment, all 800 square feet of it, has a bare-bones brick wall, walnut paneling and red vinyl booths that could never, at the Emerald, be thought of as banquettes.

“Columbus Avenue,” said Ms. Otstott, “has been turning into a strip mall, with chain stores and restaurants. Maybe the recession will help the mom-and-pops stay in business.”

But there has been no death-row reprieve for some other classics facing rent increases, like the P&G Bar, at 279 Amsterdam Avenue at 73d Street. The P&G, with the iconic neon sign that has been designated a landmark  is moving after February, to 380 Columbus Avenue at 78th Street, the former Evelyn Lounge.

Mike Campbell’s father (also Mike) opened the Emerald with his brother William. “Exactly when, we’re not sure, but it was 1943 or 1944,” Charlie Campbell said.

The Emerald has been an enduring link to the West Side’s raffish past, when Columbus and Amsterdam Avenues were populated by gin mills and where brawls among patrons, enthusiastically mediated by bruiser bartenders, were not unusual.

“We were called Spanish Harlem until the ’60s, when they put in Lincoln Center,” said Charlie Campbell. In recent decades, the clientele has gone upscale, to professionals who can afford Upper West Side housing, along with a sprinkling of loyal locals, some of them survivors of the era when “West Side Story” was a contemporary narrative.

Image The Emerald Inn, on Columbus Avenue near 69th Street. Credit... The New York Times

For years the Emerald bore a yellow and green neon sign, but about a decade ago the old sign yielded to an awning (green, necessarily). These days the front of the bar is graced only by a green neon window shamrock affixed to a blue Corona sign.