The flag will fly over the building for one day, the Fourth of July, before it is taken to Colorado to fly over the state Capitol building, The Washington Post reported Tuesday.
The idea was cooked up by hemp advocate Michael Bowman while he was lobbying Congress to include pro-hemp measures in the farm bill, the Post said.
The legislation failed, but with help from Polis, the hemp flag idea was successful.
"It's a powerful symbol," Bowman said.
The first flag created by Betsy Ross was made of hemp, the cousin of the marijuana plant that is often used to make textiles like rope and cloth.