D.C. is experiencing increased security on Metro and throughout key areas of the District in the wake of the Boston Marathon bombing, with several major landmarks seeing enhanced patrols and security sweeps.
But Tuesday's Emancipation Day parade went on as scheduled and without security incident.
"We were a little nervous, but I think if we give into that, that helps the bad people that did this," said one parade attendee.
Onlookers taking a break for lunch said the parade was the right place to be the day after a terror incident, News4's Tom Sherwood reported.
"I send all my prayers to them and everything, my sympathy, but... I mean, life is life, and we just have to get ahold of it, that's all," said a woman on the parade route.
During quiet moments at the Korean War Veterans Memorial, tourists said they were acutely aware of the bombing, but there was resolution not to give into fear of a similar attack happening here.
"Well, we were just a little bit concerned," said one tourist. "Some of our relatives from back home were calling us.... It is such a sad thing that happened, and it's just awul, but... you know, we go from day to day."
While the District had not received any credible, specific threats in the wake of the two explosions that rocked the finish line of the marathon Monday afternoon, D.C. Mayor Vincent Gray said late Monday that authorities have beefed up security as a precaution.
That's what District officials do whenever there is a national or international security concern, said Gray, standing with his public safety administrators at a press conference.
"There is a plan in place to enhance security in the area," said Metropolitan Police Chief Cathy Lanier. "There will be a visible increase in presence."
D.C. police will remain on heightened alert until further notice, according to Lanier.
Gray reminded residents to "remain vigilant," and to call 911 if they witness suspicious activity.
Early Tuesday, police blocked off roads leading to the parade route and towed a number of cars from the area. Police stood guard throughout the mid-day parade.
The White House blocked pedestrian access on parts of Pennsylvania Avenue, and tourists were briefly evacuated from the Lincoln Memorial Tuesday morning. But these security measures and sweeps were called routine, part of the increased attention that the nation's captial often experiences.
Despite the attention, officials want District residents and visitors to continue to go out and enjoy themselves.
"Come out and enjoy the events," Lanier said. "We have a very strong security plan in place."
Metro said passengers may experience random bag checks on the system and may see additional police presence, though there are no specific or credible threats to the transit system. The extra security likely will remain in place until all the facts in the Boston bombings are known, News4 transportation reporter Adam Tuss reported.
"As customers make their way onto the system this morning, they will likely notice additional patrols and additional K-9 units out on the system," said Metro spokesperson Dan Stessel early Tuesday. "We've also sent reminders to all of our... Metro employees asking for their assistance in reporting any suspicious activity or unattended items."
Specifically, Metro police are looking for unattended items.
Metro also reminded riders to report suspicious activity or packages by calling 202-962-2121.
Pennsylvania Avenue in front of the White House remains closed to pedestrian traffic Tuesday. The street shut down around 3:45 p.m. Monday.
People with hard passes could still access the White House, but the public had been pushed into Lafayette Park and elsewhere.
The Secret Service put up yellow tape to keep people off Pennsylvania Avenue in an abundance of caution following the explosions, saying expanding or contracting security perimeters is not unusual.
The Pentagon added more uniformed police officers inside and outside the installation, calling it "prudent planning."
At the U.S. Capitol and along the National Mall, the increased police presence is visible. Armed officers are patrolling landmarks popular for tourists in D.C.
Police in D.C., Prince George's County, Md., and at the University of Maryland also increased patrols. Prince George's County police increased security at all critical infrastructures but noted it is strictly precautionary. D.C. police urged residents to report any suspicious activity using using the DC Police iWATCH.
Baltimore police said Monday night that residents will see an increased police presence at events that will draw, including Tuesday night's game between the Tampa Bay Rays and the Baltimore Orioles at Camden Yards. A spokesman said police are also looking at upcoming athletic races in the city.
Maryland State Police also said troopers would be on heightened alert.
The Verizon Center issued a statement Tuesday saying it will enhance security for upcoming events.
Amtrak increased security at stations and track right-of-ways and asked passengers to report anything suspicious to 1-800-331-0008 or 911.
New Jersey Transit also is in a heightened state of alert, deploying both uniformed and plainclothes officers to patrol its system. Suspicious activity can be reported to 1-888-TIPS-NJT.
At Reagan National Airport, where some runners returned Monday after completing the Boston Marathon, security was increased and likely will remain that way through Tuesday, News4's Julie Carey reported.
Stay with NBC Washington and News4 for more on this developing story.