“River that once marked the boundary of the Wild West” crossword clue

Reveal the answer to see why it works and where this clue has appeared before.PECOS is the answer to the New York Times crossword clue “River that once marked the boundary of the Wild West”. It was last seen in the puzzle of May 24, 2025, where it runs at 1 Down and fills 5 squares. It crosses 5 other entries in that grid — those are listed below and are the quickest way to confirm the letters you already have.