VIDEO: Hundreds of protesters block entrance to Mt. Rushmore ahead of Trump rally

Hundreds of protesters blocked off the main access road to Mount Rushmore Friday night just hours before President Trump's scheduled speech at an Independence Day rally in front of the national monument.

According to the Sioux Falls Argus Leader, several protesters gathered early Friday evening around Highway 16A near Keystone and parked several vans across the road in order to form a blockade.

Soon after the blockade was formed, local authorities declared the gathering an "unlawful assembly" over a megaphone and demanded that protesters disperse. The local outlet added that at least one arrest was made and that the National Guard was called in to help clear the crowd.

Reporting live from the scene, Right Side Broadcasting Network said that protesters had slashed the tires on several of the vehicles in order to make them more difficult to move.

The Argus Leader reported that at 7:30 p.m. ET, the National Guard "fired close range smoke shells on remaining protesters." A little after 7:45 p.m. ET, the National Guard was seen moving in on the blockade wearing protective gear.

The Rapid City Journal posted a live feed of the protest.

Warning: Video may contain graphic content.

What's the background?

President Trump's decision to speak at Mount Rushmore Friday night as a kickoff to Independence Day weekend has angered many on the left, some of whom would like to see the monument removed.

Last week, two Sioux Falls tribal leaders called for the faces of the presidents carved into the rock to be removed. One tribal leader said that when his people look at the monument, they "see the faces of the men who lied, cheated and murdered innocent people whose only crime was living on the land they wanted to steal."

The president, however, has been firm in his criticism of proponents of so-called "cancel culture" and their calls for the removal of historic American statues and monuments such as Mount Rushmore.

Last week, he signed an executive order to protect monuments, memorials, and statues, punishing the vandalism or destruction of such structures with up to 10 years in prison.

According to Fox News, the president's speech is set to include much of the same rhetoric. The news site said Trump is planning to slam the "left-wing mob" for "totalitarian behavior" and speak of America as a "great and virtuous country" in his remarks.

Editor's Note: This story has been updated to include background information.