Trump inauguration live updates: Donald Trump moves swiftly to implement his new agenda

In the weeks after winning the election in November, Trump said in a post on Truth Social that imposing tariffs would be one of his first acts as president.

"On January 20th, as one of my many first Executive Orders, I will sign all necessary documents to charge Mexico and Canada a 25% Tariff on ALL products coming into the United States," he wrote.

However, he opted not to include tariffs as one of his top priorities. Instead, during his inauguration speech, he announced the creation of an External Revenue Service that would be in charge of collecting tariffs and other revenue from foreign nations.

Then, later in the evening, he expressed that his administration was "thinking in terms" of imposing 25% tariffs on Mexico and Canada on Feb. 1.

While he has also previously mentioned imposing tariffs on China, he did not mention it during his remarks in the Oval Office on Monday.

Former Proud Boys leader Enrique Tarrio, who was sentenced to 22 years in prison after his conviction of seditious conspiracy in connection with the Jan. 6 riot at the Capitol, is currently being processed for release from his cell in Louisiana following Trump's executive action Monday evening, his lawyer told ABC News.

Tarrio was notably sentenced to the longest term of imprisonment among all of the nearly 1,600 individuals charged in connection with the attack.

Click here for the full story on the Jan. 6 pardons.

Amid a back-and-forth on the future of TikTok in the U.S., Trump signaled that he thinks the U.S. should own "half" of the social media app.

He said to stay in operation in the U.S., TikTok would need to relinquish 50% of its earnings to the U.S. -- Trump did not detail how this deal would work, but said it would be a "joint venture."

The president said he changed his mind about the social media app after using it, but noted he's worried about its impacts on children.

"Because I got to use it," he said about his 180 on TikTok. "And remember, TikTok is largely about kids. Young kids. If China is gonna get information about young kids, I don't know -- to be honest with you, I think we have bigger problems than that."

Trump said that if China does not approve of the 50% sale, it would be considered a "hostile act."

While signing a slew of executive orders from the Oval Office on Monday night, Trump found a letter that outgoing President Joe Biden had left for him inside the Resolute desk.

Trump found it after Fox News' Peter Doocy asked if he'd been left a letter from Biden.

After joking about reading it aloud to the press, Trump said he would read it privately first.

Click here for a look at the tradition of presidents leaving letters for their successors.