President Trump caught flak on Wednesday after he boasted -- incorrectly -- that he is "building a beautiful wall" in Colorado, a state that does not border Mexico.

The state's Democratic Gov. Jared Polis mocked Trump for the gaffe on Twitter, saying: "Well this is awkward... Colorado doesn't border Mexico. Good thing Colorado now offers free full day kindergarten so our kids can learn basic geography."

Trump visited Pittsburgh on Wednesday to speak at the annual Shale Insight Conference, where he addressed an audience of mostly blue-collar workers from Pennsylvania, Ohio and West Virginia. He boasted construction of a border wall between the U.S. and Mexico, which he said is necessary to stem the flow of illegal immigrants and drugs into America, and proceeded to list the bordering states, mistakenly including Colorado.

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"You know why we're going to win New Mexico? Because they want safety on their border. And they didn't have it. And we're building a wall on the border of New Mexico," Trump said. "And we're building a wall in Colorado. We're building a beautiful wall, a big one that really works. ... And we're building a wall in Texas. And we're not building a wall in Kansas, but they get the benefit of the walls that we just mentioned. And Louisiana's incredible."

Rep. Diana DeGette, D-Colo., jumped on the verbal gaffe: "Is NEW Mexico gonna pay for it?"

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Sen. Michael Bennet, D-Colo., responded on Twitter with a zing of his own: "Let me repeat: There isn’t an elected leader from the state of Colorado who would support using eminent domain to steal the property of our farmers and ranchers to build a medieval wall."