 The Rocky Mountain Front is a significant feature in the state's north-central portion, and isolated island ranges that interrupt the prairie landscape common in the central and eastern parts of the state.About 60 percent of the state is prairie, part of the northern Great Plains.The Bitterroot Mountains—one of the longest continuous ranges in the Rocky Mountain chain from Alaska to Mexico—along with smaller ranges, including the Coeur d'Alene Mountains and the Cabinet Mountains, divide the state from Idaho.