So much change has come to South Boston in recent years. Now it’s even coming for what’s billed as “the Oldest Restaurant & Bar in Southie.”

The owner of Amrheins, which has held down the corner of West Broadway and A Street since 1890, has put the classy neighborhood joint, and its prized parking lot next door, up for sale. The half-acre site could fetch $20 million or more, real estate experts say, and the new owner almost certainly will replace the brick and wood buildings that house Amrheins with something along the lines of the mid-rise apartments that have transformed Broadway’s Lower End.

The broker handling the sale for Amrheins owner Steve Mulrey said he aims to have a buyer lined up this fall. Mulrey, whose family has owned the restaurant since the 1950s, declined to comment on the decision to sell. But Tom Greeley, managing director at real estate brokerage Newmark Knight Frank, said Mulrey hopes that any new development — which likely wouldn’t break ground for at least a year or two — might include space for a new incarnation of the restaurant.

“This does not mean an abrupt close to Amrheins,” Greeley said. “One of [Mulrey’s] highest priorities is making sure he does right by his employees and valued customers.”

As word of the impending sale — first reported in the real estate publication The Real Reporter — spread on Wednesday, a few of those customers said they will be sorry to see the end of Amrheins, with its dark wood, high booths, and a wide-ranging menu that requires serious perusing.

Carolee Salerno said she comes up from Cape Cod for a meal at the restaurant about four times a year. She especially likes to bring friends in the fall, when Amrheins offers risotto served in a pumpkin.

“It’s sad to hear,” she said after lunch Wednesday. “If I have a choice to go somewhere new, or somewhere with history, I will always choose the history.”

And Amrheins has plenty of history. In addition to holding the title of oldest bar in South Boston, it claims to have both the first draft beer pump in the city and an ornate hand-carved wooden bar that is the oldest of its kind in America. It also holds a place in the memories of generations of residents of the tight-knit neighborhood around it.

Lifelong Lower Ender Eileen Murphy used to walk by on her way to the old Cardinal Cushing High School, which itself was converted to luxury condos a decade ago. She recalls attending countless baby showers, graduation parties, and wakes at Amrheins.

“Milestones were marked there. It was a gathering place for many, many families for stuff like that,” Murphy said. “It’s not that the newer places aren’t nice. It’s just a different feel.”

The place also holds a spot in Boston political lore. The function room is named for former mayor James Michael Curley, and many local pols — from former city councilor Dapper O’Neill to US Representative Stephen Lynch — often held court there. It has long been a popular stop on the fund-raising circuit, and for endorsement speeches for candidates eager to gain some Southie cred.

But the neighborhood has evolved, said Maureen Dahill, author of the popular Caught in Southie blog. Newer, of-the-moment restaurants have moved in, and a development boom has driven land prices so high that, for many longtime establishments, their real estate is worth more than their business. Meanwhile, many of the families who made up Amrheins’ core clientele have done the same math, trading their old Southie homes for roomier, quieter quarters in the suburbs.

“I still think it appeals mainly to old-school Southie, maybe even old-school Southie who has moved out of the neighborhood,” Dahill said. “One reason they come back is because it’s the only place that has any parking.”

Indeed, Amrheins’ parking lot — space so rare in Boston that the restaurant touts “free on-site parking” on its website — is a central reason why the location is such an attractive site for developers, Greeley said. With the lot, Mulrey controls about a half-acre of prime real estate along Broadway, a site slightly larger than the gas station property across the street where the city last year approved a six-story, 65-unit apartment building. He also owns Mul’s Diner, kitty-corner from Amrheins at Broadway and A Street. That property is not for sale, Greeley said.

Greeley said he has heard from housing developers interested in Amrheins, but also from people who would build an office building or lab space on the site, a reflection of growing interest in the neighborhood as a place where people can work close to public transit. Either way, he’s expecting a hefty sale price and a quick closing.

“This is an incredibly exciting piece of real estate, not just in Southie but in the whole city,” Greeley said. “The site is just primed for something big.”

And, after 128 years of comfort food and camaraderie, something different.