Welles Remy Crowther was born the first of three children. His parents, Jefferson and Allison, raised him and his two younger sisters, Honor and Paige, in the New York City suburb of Nyack, New York. Through his father, he is a grandson of Bosley Crowther, film critic of The New York Times from 1940 to 1967. As a child, Crowther saw his father getting dressed for church and wrapping a small comb in a blue or red bandana he kept it in his right hip pocket. When Welles was 6 years old, his father gave him a red bandana that would become Crowther's trademark which he wore under all of his sports uniforms in high school.
At 16, Crowther joined his father as a volunteer firefighter, becoming a junior member of the Empire Hook and Ladder Company. He later attended Boston College, where he played lacrosse, In 1999, Crowther graduated with honors with a degree in economics. He subsequently moved to New York City, taking a job as an equities trader for Sandler O'Neill and Partners, settling into an office on the 104th floor of South Tower of the World Trade Center. He later entertained dreams of joining the FDNY or the FBI or CIA.
On September 11, 2001, minutes after United Airlines Flight 175 struck the South Tower between floors 78 and 85 at 9:03 a.m., Crowther called his mother from his office at 9:12 a.m., leaving the message, "Mom, this is Welles. I wanted you to know that I'm OK." Crowther made his way to the 78th floor sky lobby, where he encountered a group of survivors, including a badly burned Ling Young, who worked on the 86th floor in New York's Department of Taxation and Finance. Young had been one of approximately 200 people waiting at a bank of elevators to evacuate when the plane hit the tower, and one of the few survivors. Crowther, carrying a young woman on his back, directed them to the one working stairway. The survivors followed him 17 floors down, where he dropped off the woman he was carrying before heading back upstairs to assist others. By the time he returned to the 78th floor, he had a bandana around his nose and mouth to protect him from smoke and haze. He found another group of survivors, which included AON Corp. Employee Judy Wein, who worked on the 103rd floor and was in pain from a broken arm, cracked ribs and a punctured lung. According to Wein, Crowther assisted in putting out fires and administering first aid. He then announced to that group, "Everyone who can stand, stand now. If you can help others, do so." He directed this group downstairs as well. As occupants of the Tower headed for the street, Crowther returned up the stairs to help others. He was last seen doing so with members of the FDNY before the South Tower collapsed at 9:59 a.m.
Crowther's body was found on March 19, 2002, alongside several firefighters and emergency workers bunched in a suspected command post in the South Tower lobby. The New York medical examiner's office said his body was found intact, with no signs of burns, and that authorities speculated that he was aiding the rescue effort as a civilian usher when the building collapsed. Crowther's family was unaware of the details of Crowther's activities between his last phone call to his mother and his death, until Allison Crowther read Judy Wein's firsthand account in The New York Times of being saved by a man in a red bandana, which led to Allison meeting with the people Welles had saved, including Wein and Young; they confirmed from photographs the identity of the man who aided them. According to survivor accounts, Crowther saved as many as 18 people following the attacks.
Crowther's parents, with the support of a Michigan foundation, created the Red Bandana Project, a character-development program for classrooms, sports teams, camps and youth programs. The family also established the Welles Remy Crowther Charitable Trust, with which they fund charitable work.
The Welles Remy Crowther Red Bandana Run, a 5-kilometer road race, is held every October at Boston College.
In 2006, Crowther was posthumously named an honorary New York City firefighter by Commissioner Nicholas Scoppetta.
That same year, Crowther's Boston College lacrosse teammate, Tyler Jewell, wore a red bandana in honor of Crowther when he competed as a member of the United States snowboarding team in the 2006 Winter Olympics.
During the September 10, 2011, Central Florida-Boston College football game in Orlando, Florida, a day before the 10th anniversary of the September 11 attacks, both schools honored Crowther. Boston College players wore helmet stickers featuring Crowther's signature red bandana during the game, and Crowther's sisters, Honor Fagan and Paige Crowther, were introduced to the crowd during the third quarter. On September 13, 2014, Boston College played the University of Southern California (USC) and the team wore uniforms symbolizing Crowther's red bandana, including a helmet stripe, cleats and gloves that have a red bandana pattern. Boston College then defeated the ninth-ranked Trojans 37–31 in a stunning upset.
At the National 9/11 Memorial, Crowther is memorialized at the South Pool, on Panel S-50. President Barack Obama, during his May 15, 2014, dedication of the museum, said of Crowther, "They didn't know his name. They didn't know where he came from. But they knew their lives had been saved by the man in the red bandana. He called for fire extinguishers to fight back the flames. He tended to the wounded. He led those survivors down the stairs to safety, and carried a woman on his shoulders down 17 flights. Then he went back. Back up all those flights. Then back down again, bringing more wounded to safety. Until that moment when the tower fell." One of Crowther's bandanas is on display at the museum.
He was the subject of the 2017 feature documentary Man in Red Bandana.