Staten Island may no longer qualify as the forgotten borough, at least among real estate agents.

After months of watching housing prices rise in Richmond County, some of the larger Manhattan-based real estate firms are expanding their reach across New York Harbor.

Local agents said they welcomed the move as a sign of the market’s ascent, particularly in the North Shore neighborhoods. But some residents viewed the encroachment as another harbinger of gentrification.

“Everyone wants a piece of the pie,” said Holly Wiesner Olivieri, who owns a brokerage company in St. George. “That comes with progress.”

Earlier this month, Keller Williams opened an office in Midland Beach. And after months of studying the market, Keller Williams’ TriBeCa-based Thomas-Gabay team started working in Staten Island this September.

The duo said new housing developments, a planned outlet mall and the construction of what has been billed as the tallest observation wheel in the Western Hemisphere have helped put the North Shore area on the radar of New Yorkers searching for a bargain not easily found in other boroughs.

“We’re kind of hoping that other people wait,” Millard Thomas, of Keller Williams, said of other Manhattan colleagues following his lead. “But we know that it would kind of be idiotic for them not to get involved.”

Lisa Lonuzzi, a Corcoran associate broker based in Brooklyn, said she has returned to the Staten Island market, where she worked for years with another company before leaving it in 2008 to focus on Brooklyn full time. Lonuzzi said she has invited brokers from the major outfits in Manhattan and Brooklyn to tour the borough.

“I’m very avidly trying to push Staten Island to become not the ‘forgotten borough,’” she said.

Local brokers said they were not intimidated by new companies moving in. Olivieri said she has a level of local expertise that sets her apart and has proven pivotal to helping clients unfamiliar with the area.

And Jon Salmon, who heads up the Salmon Real Estate firm his father started, said he has seen the larger firms make a go at Staten Island before. Salmon said he welcomes them, although they may not stick around.

“Competition means there’s a need,” he said.

Indeed, housing costs have spiked on Staten Island. The average monthly rent has grown to $2,239 this April from $1,828 in April 2012, according to Zillow. The average sales price for a one- to three-family home rose 10% from the first quarter of 2016 to 2017, according to the Real Estate Board of New York.

Prices rose in many parts of the borough, but agents said the North Shore’s strength was notable because it has historically not been on pace with the rest of the island.

Robin McGill, 66, said she has noticed new realty companies and viewed the trend as a part of the same cycle that transformed the market in Harlem and Bedford-Stuyvesant.

“You can see the signs — you’re starting to see companies you never saw before,” said McGill, who has lived between St. George and New Brighton for 30 years. “They’re starting to come in. Rents are starting to go higher. A lot of low-income people seem to be being displaced. But that’s what it’s been all my life — I’m a New Yorker.”

James Regan, who has lived on Avon Place in Tompkinsville for more than 20 years, said the Manhattan firms are following the money. He said people priced out of Brooklyn and other boroughs have been moving to the area for years.

“I have a good job. I should be able to live here comfortably,” said Regan, who works for the city Department of Environmental Protection, and has had friends who had to move to New Jersey or Pocono, Pennsylvania, when they could not afford rents in Staten Island. “I’m thinking about buying a house out there [Pocono].”