The S&P 500 closed in record territory, surpassing its previous all-time best of 3,027.98 that was set in July. It was the 103rd record close since President Trump's election victory and 94th since he took office.

"The S&P just hit an ALL TIME HIGH," President Trump tweeted Monday. "This is a big win for jobs, 401-K’s, and, frankly, EVERYONE! Our Country is doing great."

However, the major averages slipped off their best levels of the session after the House of Representatives announced its vote to press forward with an impeachment inquiry will take place this week.

The S&P 500 gained 0.56 percent on its way to booking a record high of 3,039.33. The Dow Jones Industrial Average and Nasdaq closed up 0.49 percent and 1.01 percent, respectively, and are on their doorstep of their own records.

Early sentiment was helped by President Trump telling reporters that a phase one trade deal with China was "ahead of schedule" to be signed at the Asia-Pacific Economic Cooperation summit in Chile next month.

Additionally, the European Union agreed to postpone the United Kingdom’s exit from the bloc for three months, paving the way for a departure on, or before, Jan. 31, 2020. It's the third time that Brexit has been delayed. The U.K. was originally supposed to leave the E.U. on Mar. 29, 2019.

Tiffany & Co. shares surged after the fashion powerhouse LVMH made a takeover offer of about $120 a share, or $14.5 billion, according to The Wall Street Journal.