The WTC Cortlandt line opened over the weekend. It features a mosaic with text from the Declaration of Independence and the United Nations' Universal Declaration of Human Rights.
"The opening of WTC Cortlandt returns a subway station to a vibrant neighborhood and represents a major milestone in the recovery and growth of downtown Manhattan," MTA Chairman Joseph Lhota said.
The WTC station was destroyed and buried by debris after both World Trade Center towers collapsed on Sept. 11, 2001. The majority of the new station was built on the footprint of the old station, measuring 700 feet long and 47 feet wide.
Tuesday is the 17th anniversary of the deadliest terrorist attacks on U.S. soil, which killed nearly 3,000 people in Manhattan and at the Pentagon in Arlington, Va.
Forty passengers and crew also died aboard United Airlines Flight 93, which crashed in a field near Pittsburgh. Sunday, a memorial was unveiled a couple miles north of Shanksville, Pa., to honor those on the flight.
Families of the victims gathered at the crash site to mark the opening of the Tower of Voices, a 93-foot concrete and steel structure with wind chimes -- each making a unique sound.
"Together their voices will ring into perpetuity with this beautiful Somerset County, Pa., wind," park superintendent Stephen Clark said.
Some of the passengers and crew aboard the fourth hijacked airliner were hailed as heroes that day -- for attempting to retake control of the plane after they'd learned of the attacks in New York and Washington, D.C.
"When they learned that, it galvanized them as a group," Clark said. "They said, 'We're not going back to any airport. This is a suicide mission.'"
According to the 9/11 Commission Report, the terrorists intended to fly Flight 93 to Washington, D.C. Their intended target, investigators believe, was the U.S. Capitol.
The Tower of Voices is the final phase in the Flight 93 National Memorial, which also includes a memorial plaza and a visitors center.
Although the official toll from the attacks is just under 3,000, New York City authorities say that toll is still growing continuously.
"To this day, we're still losing officers each and every year from the effects of 9/11," New York City Police Chief Terence Monahan told ABC News.
In a ceremony last week, the Fire Department of New York added 18 firefighters who died over the past year to a memorial wall at FDNY headquarters honoring the fallen from Sept. 11. Officials say those 18 are among 187 firefighters who have died from Sept. 11-related illnesses.
"Our World Trade Center Memorial is a symbol of our sacrifice, our dedication and above all else our bravery that is the hallmark of the FDNY," Fire Chief James Leonard said. "Those we're honoring toiled at that site of such terrible destruction. They worked long, difficult, painful hours sifting through the rubble to search for those killed."
The September 11th Victims Compensation Fund has determined more than 20,874 people are eligible for compensation. The fund, established by Congress in 2011, has so far awarded $4.3 billion. The list includes more than 16,000 responders who performed recovery, demolition and debris cleanup in the aftermath of the attack.