Officers have had hours extended as they were deployed, making sure they are highly visible around government buildings and tourist-friendly attractions like the art museum and the historic district.
Some Bostonians, in Philadelphia for several days, told Action News they are trying to feel calm at Independence Mall after seeing the carnage back home.
"I do see security around and I feel safe," Anne Schwartz said.
There were many international travelers on the Mall Tuesday who came from other countries where they've learned to live with the threat of terrorism.
One woman, from Pakistan, said the Taliban frequently uses pressure cooker explosives, like the ones believed to have been set off in Boston on Monday.
"I used to think terrorism was in Islamic countries like Pakistan, but I came to know that it's everywhere," said Shehdadi Shah.
The Philadelphia Police Bomb Squad was very busy on Tuesday, going on several calls from those who saw abandoned packages and called - deciding to be safe rather than sorry.
No explosive material has been found in Philadelphia.