The third victim, a man, was brought up on an ATV.
One of two women, 45-year-old Loida Campo of Schenectady, was so badly injured she had to be flown by helicopter to Albany Medical Center Hospital.
The three were hurt after crashing near the bottom of a grassy section of the gorge.
None of the injuries were life-threatening, though medical personnel said Campo suffered a severe gash to her head.
Campo and the others, Joseph Pitt of Schenectady and Melinda Tirado of Brooklyn, were riding on the ATV on a hillside clearing beneath Niagara Mohawk power lines when the driver lost control of the four-wheeler at approximately 7 p.m. They weren't wearing helmets, police said.
"The ATV did a roll over," said Chief John Tobiassen of the Plotterkill Volunteer Fire Department.
Pitt ran up the ravine to a house on Coplon Road to report the crash, then returned to the scene several hundred feet below.
"I was washing the car and then everybody started coming up," Coplon Road resident Tyler Cuomo said of the dozens of firefighters that assembled in his father's yard next door.
In the gorge, a dramatic rescue unfolded as dozens of firefighters from most of the town's fire districts converged on the site.
Near the bottom of the gorge, paramedics tended to the riders' various injuries as teams of firefighters gathered at spots on the hillside to take turns carrying the stretchers up the treacherous path.
Firefighters prepared to use ropes and pulleys to carry the patients to the top, but opted to simply take turns carrying them. The firefighters went cautiously up the hillside, taking care not to slip on loose soil or grass made slick by the evening dew.
"Luckily it was in the middle of the trail," said Gary Miller, first-assistant chief of the South Schenectady Fire Department. "This is dangerous as it is just walking and carrying somebody. It's not good."
One by one, the women were carried up the hillside and loaded into a waiting ambulance. Campo was driven a short distance to a field where the Albany Medflight ambulance flew her to Albany Med. The others were taken to Ellis Hospital in Schenectady by ambulance.
The Plotter Kill, a tributary of the Mohawk River, flows through a rugged gorge and drops 900 feet in a gradual 3.5 mile descent from Rynex Corners to the river. The 632-acre preserve, owned by Schenectady County, contains three waterfalls: The Upper Falls is 60 feet; the Lower Falls and the Rynex Creek Falls are both 40 feet.
The preserve is a popular spot for hikers and others, but firefighters said people often have to be rescued from the gorge.
"It's normally people getting lost," Tobiassen said, though he and other firefighters added that injured hikers have also been rescued.
Pitt and Tirado were being treated late Sunday for minor injuries. Their exact ages were unavailable, but authorities at the scene said they are in their 20s.
The use of ATVs or other such vehicles is forbidden on the NiMo property, authorities said. Police were investigating the accident late Sunday.
