Portion of Rewind Replay's Article "Rockstar never identified what state Red Dead Redemption is based off of, but later in the game John Marston travels to Mexico via the fictional San Luis river in the border between the United States and Mexico. After quickly researching Google maps, the only river dividing the United States and Mexico is Rio Grande which starts in Colorado, cuts through New Mexico, then Texas, and ends in the Gulf of Mexico. Assuming that the river is not fictional we can assume that Red Dead Redemption is set in Texas. Furthermore, Red Dead Redemption is set in 1911, one year before Arizona entered the Union. Therefore the only other possible state the game could have been set in is New Mexico."