The Laurel hotels where they stayed have been renovated and still attract an occasional tourist with a camera.
The restaurant where they ate pizza has changed owners three times, and the new one says he knows nothing of its infamous former customers. The tiny airport in Bowie that refused to rent them airplanes struggles under the onus of heightened security rules and threatening calls from strangers.
Before they crashed seized planes and changed the world, the Sept. 11 terrorists - at least seven of the 19 - lived out their last days in Maryland, lifting weights, washing clothes, looking at pornography, buying groceries and polishing their flying skills.
Five left the state Sept. 10, spending a final night in Virginia before boarding American Airlines Flight 77 at Dulles Airport and crashing it into the Pentagon. One departed Sept. 9, drove to Newark, N.J., and got on United Airlines Flight 93, which crashed into rural Pennsylvania after a struggle between passengers and hijackers. Mohamed Atta, the ringleader, flew in on Sept. 7 and flew out Sept. 9.
They barely spoke to anyone, even those who greeted them, and they left behind little in the way of evidence for investigators who would follow, combing for clues.
But five years later, their chance encounters with those who met them have left an indelible mark.
"It's almost a curse," said Marcel Bernard, chief flight instructor at Freeway Airport in Bowie, where the hijacker pilot of Flight 77 went up a few times with instructors. "It's haunting in a way, to always have to think about this."
Bernard has told the story maybe 100 times, he says, to the FBI and myriad federal agencies, to the news media, to curious flight students and the occasional 9/11 conspiracy theorist.
Hani Hanjour came to Freeway Airport and asked to rent a plane. He went up with two flight instructors on three occasions, but Bernard eventually refused to rent him a plane because he barely spoke English - a requirement for flight certifications - and because of his poor flying skills.
The two last spoke on the phone a few weeks before the attacks, when Hanjour complained about an $80 no-show charge. Hanjour never paid.
After Sept. 11, when details about the terrorists surfaced, Bernard and other Freeway employees received "hate calls" laced with accusatory expletives.
Freeway lost $600,000 in revenue after the Sept. 11 attacks because it and other small airports near Washington were closed for 13 weeks. Now, with a list of restrictions that limit where instructors can fly with students and when they can take off, Freeway isn't making much money.
"A lot could be said to the fact that it was airlines, not general aviation, whose security was breached," he said. "We are the scapegoat. ... And so here we are now, our business is in jeopardy, our livelihood in jeopardy."
He says things carefully, but words spill out as he talks about Hanjour.
"I'm not comfortable knowing I was close to someone who did something so evil and had such disrespect for life," Bernard said. "Of course, I wish, in hindsight, that I would have known something. In those days, suicide hijackers didn't exist."
Bernard and others who saw the hijackers in the weeks before the attacks are left to wonder: Was there anything I could have done?
The Maryland State Police conducted a review of a traffic stop by one of its officers, who pulled over one of the terrorists in the days preceding the attacks, to see if the officer should have done anything more. The conclusion: no.
Trooper Joseph Catalano stopped Ziad Jarrah, believed to have piloted Flight 93, shortly after midnight Sept. 9 and gave him a speeding ticket for traveling 90 mph in a 65-mph zone just north of the Susquehanna Bridge on I-95.
In a video of the encounter released in 2002, Catalano is seen asking Jarrah about his Springfield, Va., address, checking the license plates of his New Jersey-registered Mitsubishi and giving Jarrah a ticket. For much of the seven-minute tape, "I'm Already There" - a country hit by Lonestar - can be heard faintly playing in the background.
Catalano gave Jarrah the ticket and said, "Here's your information; you're free to go."
Investigators recovered the ticket in the glove compartment of the Mitsubishi, left at the Newark airport.
After a review, Catalano was found to have acted according to procedure. The terrorist was not wanted for any crimes and was not on a watch list, so a background check would have been fruitless. The trooper checked to be sure the car was not stolen, which it wasn't.
He remains on the force at the same rank, a trooper 1st class. He declined, through a state police spokesman, to comment for this story.
A man who answered the phone at Congressional Air Charters of Gaithersburg declined to give his name and said the company no longer gives flight instruction. On July 20, 2001, Hanjour - likely accompanied by Nawaf al-Hazmi, another member of the Flight 77 team - completed a "challenging certification flight" supervised by an instructor from Congressional, according to the report of the 9/11 Commission.
The strip where the hotels are located appeared a bit run down in 2001 but is now showing signs of gentrification, with several luxury apartment complexes set to go up soon.
Some of the places the terrorists frequented are visited now and then by tourists. People come to take pictures, stay in the same hotel rooms or even buy box cutters from area stores that sell them. Box cutters are believed to have been used by the terrorists to disable the flight crews and take over the planes.
The Pin-Del Motel, where Jarrah and Nawaf al-Hazmi stayed for one night each, was converted 2 1/2 months ago into a Days Inn.
The Valencia Motel, where Hanjour and four others stayed from late August to Sept. 10, still exists, but the building where they stayed has been demolished and replaced. It was in a room there that investigators found an aerial photo slide of Washington left behind by the plotters.
Suresh Patel, who owns and operates the new Days Inn with his wife and son, and also operated the Pin-Del Motel, said people sometimes ask to stay in the same rooms - which have now been totally renovated.
FBI agents came to visit Tuesday, just to let him know that he could report anything suspicious to them.
Patel said he felt terrible when he saw their faces on TV. They appeared normal, he says.
"They were normal people," he said. "They didn't keep a high profile. I didn't have any doubt about these people."
After Sept. 11, some customers looked at him suspiciously. He is from India, but some connected him with the men who stayed in his hotel, although investigators found no such evidence.
"People come in for registration, I tell them, 'This is the rate,' and then they tell me: 'You are all terrorists, and you invited terrorists here,'" Patel said. "I say, 'That's nonsense, you don't know what the hell you are talking about.' Everybody comes here to make a living, that's it."
Hanjour and the other four on the Flight 77 team worked out at a Gold's Gym in Greenbelt between Sept. 2 and Sept. 6, awkwardly lifting weights and using resistance machines. Hanjour told a gym receptionist that his first name means "warrior" in Arabic, although scholars say it means "content."
Majed Moqed, one of the Flight 77 hijackers, nervously perused adult movies and books at a store near the Valencia and also in Beltsville at least three times in August, according to media accounts.
"Did they really eat here?" asked Keith Jordan, 27, as he sat at Pizza Time, a small place with one table in a shopping center near the Valencia. He learned that the hijackers ate pizza there, perhaps at the very table where he sat.
Pizza Time has gone through three owners since 2001, and Babu Meah, its current owner, said he knows nothing about the hijackers.
Brad Kay, owner of the Superpawn, a small shop about 50 yards from the Valencia, said, "I'm sure they came here."
Like most pawn shops, Kay's store is filled to the brim with stray artifacts of people's lives - jewelry, electronics, baseball cards. And box cutters. He wonders if he sold them the box cutters.
The 9/11 Commission Report says the hijackers bought box cutters in the days before the attacks, although it doesn't say where. An FBI spokeswoman said she couldn't comment on where they were bought, because "Penttbom" - an FBI code name for the 9/11 investigation - is still an open case.
"You wish you could go back in time and change things, and it may not ever have happened. Things would be so different," Kay said. "But ... it proves that anyone determined to cause that sort of damage can just blend in - slip in and not be noticed. It's weird, you know?"
To see a video of the traffic stop, go to baltimoresun.com/jarrah.