The weekend crash was characterised by authorities as the deadliest US transportation accident in nearly a decade.
The crash turned a relaxed Saturday afternoon to horror at a rural spot popular with tourists viewing the region's fall foliage.
Relatives said the limousine was carrying the sisters and their friends to a 30th birthday celebration for the youngest.
"They were wonderful girls," said their aunt, Barbara Douglas, speaking with reporters on Sunday.
"They'd do anything for you and they were very close to each other and they loved their family."
Ms Douglas said three of the sisters were with their husbands, and she identified them as Amy and Axel Steenburg, Abigail and Adam Jackson, Mary and Rob Dyson and Allison King.
"They did the responsible thing getting a limo so they wouldn't have to drive anywhere," she said, adding the couples had several children between them who they left at home.
The 2001 Ford Excursion limousine was traveling southwest on Route 30 in Schoharie, about 170 miles north of New York City, when it failed to stop at 2pm local time on Saturday at a T-junction, State Police First Deputy Superintendent Christopher Fiore said at a news conference in Latham, New York.
It went across the road and hit an unoccupied vehicle parked at the Apple Barrel Country Store, killing the limousine driver, the 17 passengers, and two people outside the vehicle.
The crash "sounded like an explosion," said Linda Riley, of nearby Schenectady, who was on a shopping trip with her sisters.
The store manager, Jessica Kirby, told The New York Times the limo was coming down a hill at "probably over 60 mph".
The National Transportation Safety Board (NTSB) is investigating.
"This is one of the biggest losses of life that we've seen in a long, long time," NTSB chairman Robert Sumwalt said.
It is the deadliest transportation accident since February 2009, when Colgan Air Flight 3407 crashed near Buffalo, New York, killing 50 people, Mr Sumwalt said.
At the news conference, Mr Fiore did not comment on the limo's speed, or whether the limo occupants were wearing seat belts.
Authorities did not release the names of the victims or speculate on what caused the limo to run the stop sign. Autopsies were being conducted.
Valerie Abeling said her 34-year-old niece Erin Vertucci was among the victims, along with Ms Vertucci's newlywed husband, 30-year-old Shane McGowan.
"She was a beautiful, sweet soul; he was too," Ms Abeling said.
The couple was married in June at a "beautiful wedding" in upstate New York, Ms Abeling said. "They had everything going for them."
Ms Vertucci, who grew up in Amsterdam, New York, was an administrative assistant at St Mary's Healthcare in Amsterdam, Ms Abeling said.