"My situation is, I want to be a witness to history," the Maryland Democrat told CNN's Chris Cuomo on "New Day." "My forefathers have worked hard to give me and others these opportunities."
Dozens of Democratic lawmakers are boycotting the inauguration, particularly after revelations of Russia's alleged meddling in the 2016 election and Trump's rebuke of civil rights icon Rep. John Lewis for saying he didn't believe Trump's presidency was legitimate.
Some members have said they will be protesting in Washington or in their home districts instead.
Cummings said he understands his colleagues' decision to protest.
"I think that they should do what they believe in their hearts," he said.
"You gotta understand that we members of Congress have a lot of information that the public does not have," he added. "If the public knew what members of Congress knew ... The information will come out later at some point. Then the public will fully understand."
Congress needs to do more to investigate Russia's involvement in the election and FBI Director Jim Comey's role in Hillary Clinton's email scandal, Cummings said.
The Justice Department's inspector general is looking into
how the FBI handled the investigation of former Secretary of State Hillary Clinton's private email server during the 2016 presidential campaign.
"This is our watch and we have to protect this democracy," said Cummings, the top Democrat on the Committee of Oversight and Government Reform. "This to me is bigger than President-elect Trump. I'm concerned that we are moving slowly but surely towards a crisis of legitimacy with regards to our core institutions."