Context

This famous line was spoken by U.S. President Ronald Reagan at the Brandenburg Gate of the Berlin Wall in West Berlin, Germany on June 12, 1987. Gorbachev = Mikhail Gorbachev.

The Berlin Wall, consciously uncoupled West Berlin and West Germany from East Berlin and East Germany during the Cold War from 1961 to 1989.

On June 12, 1987, Ronald Reagan, Bonzo the chimp's co-star, told that guy who does a Cossack dance with Zangief at the end of Street Fighter II to tear down the Berlin Wall.

With the help of Bruce Springsteen and David Hasselhoff, they eventually did.

Where you've heard it

The 25th anniversary of the fall of the Wall was in 2014, so you heard it a lot then. 

Additional Notable References:

• Family Guy portrayed Reagan trying to tear down a wall himself with his patented Reagan Smash.
• The PC game Civilization 5 has an achievement called "Tear Down This Wall." 
• So does World of Warcraft. 
• "Tear down this wall" is a useful card to play in the popular Cold War board game Twilight Struggle. 
• For some reason, WIRED equates Cold War Berlin with Facebook. 

Pretentious Factor

If you were to drop this quote at a dinner party, would you get an in-unison "awww" or would everyone roll their eyes and never invite you back? Here it is, on a scale of 1-10.

The U.S. thought it was a good idea to divide Germany up into bite-size pieces at the Potsdam Conference in 1945, so it's a little sanctimonious to be champions of freedom decades later.