Barricades now surround the Pennsylvania State Capitol Complex in Harrisburg with extra security on duty, and steps are being taken as the FBI continues to warn of potential violent disruptions at capitals in all 50 states.
Governor Tom Wolf ordered the Capitol Complex to close through Thursday.
Cities have been on alert since January 6 when a mob supporting President Donald Trump stormed the U.S. Capitol in a deadly riot.
RELATED: FBI warns public, law enforcement of 'substantial' danger of explosive devices at protests
Since then, police in Pennsylvania, New Jersey and Delaware have teamed up with the FBI and National Guard in anticipation of potential protests. Some businesses have already shut down in Trenton as a precaution.
Trenton Mayor Reed Gusciora says they aren't taking anything for granted and is urging people who are thinking about protesting violently to stay home.
"I think that lessons were learned from the U.S. Capitol, also, a lot of spouses telling their other spouses to stay home and not to get caught up in the demonstrations," Gusciora said.
RELATED: New Jersey increases security after FBI warning
In Delaware on Monday, fencing and barricades were put up as a group of Trump supporters protested peacefully.
Gov. Phil Murphy on Friday ordered state employees to work remotely on Wednesday when President-elect Joe Biden is inaugurated.
In Philadelphia, all members of the police department are on notice to work through Thursday. The police commissioner said there are no specific threats to the city at this time, but officers are prepared.
Joe Sullivan is a former Philadelphia police deputy commissioner of patrol operations, who also served as chief inspector of Homeland Security. He's handled events like the Papal Visit and DNC Convention and said cities had to take the FBI memo seriously especially in light of what officials knew prior to January 6, but may have not disclosed.
RELATED: Retired firefighter from Chester, Pa. accused of throwing fire extinguisher at police officers during Capitol riot
"What the FBI does and I think it's the right thing, is put it out and allow individual municipalities to evaluate it for themselves and decide what is the right course of action," said Sullivan. "It's better that they over plan than under plan."
Sullivan says overplanning is important.
"When you have to call for help in the middle of a crisis, help is not going to get there in time to make a difference," he said.
Washington, D.C. has been transformed into a virtual fortress ahead of Biden's inauguration. There are currently more than 21,500 National Guard troops in the nation's capital.
WATCH: More than 20,000 National Guard troops standing guard ahead of inauguration
Command Sergeant Major Michael Brooks from the District of Columbia National Guard says they are hoping for the best but prepared for the worst.
"We're here to protect the citizens of the United States just as much as we are the seat of our government. So, no one should fear us unless they have ill-will in their hearts," said Brooks.
The security measures go far beyond the busloads of National Guard members still arriving at a steady clip.
There is barricade fencing topped with razor wire blocking off entire sections of D.C.
Bomb-sniffing dogs are being employed to help ensure the safety of packages and vehicles entering secured areas.
Secretary of the Army Ryan McCarthy has confirmed they are even screening the troops on the ground for any possible insider threat.
"It's the unknown. We've also been vetting them through the FBI. We're continually going through the process and taking second, third looks at every one of the individuals assigned to this operation," said McCarthy.
SEE ALSO: FBI vetting Guard troops in DC amid fears of insider attack ahead of inauguration
Maj. Gen. William Walker, the commanding general of the D.C. National Guard, says that the vetting process will continue all the way up to Inauguration Day.
"It's just another layer and then a layer on top of that just to be absolutely certain. But everyone joining the military is screened in, and for an event like this, you're screened out," said Walker.
Roughly 25,000 National Guard troops are expected to be in place in Washington overseeing the inauguration.