Question: Which states are Mountain States in the Northwestern region?
Context: Rocky Mountain National Park is a United States national park located approximately 76 mi northwest of Denver International Airport in north-central Colorado, within the Front Range of the Rocky Mountains.  The park is situated between the towns of Estes Park to the east and Grand Lake to the west.  The eastern and westerns slopes of the Continental Divide run directly through the center of the park with the headwaters of the Colorado River located in the park's northwestern region.  The main features of the park include mountains, alpine lakes and a wide variety of wildlife within various climates and environments, from wooded forests to mountain tundra. The Northwestern United States is an informal geographic region of the United States.  The region consistently includes the states of Oregon, Washington, and Idaho—and usually Montana and Wyoming.  Some sources include southeast Alaska in the Northwest.  The related but distinct term "Pacific Northwest" generally excludes areas from the Rockies eastward. Yutaka Yaguchi (born November 14, 1932) is the Chief Instructor and Chairman of the International Shotokan Karate Federation (ISKF) Mountain States Region.  He was born in Hiroshima, Japan, in 1932 and began karate training in 1952.  He later tested under masters Gichin Funakoshi for his 1st "dan" black belt and Masatoshi Nakayama for his 2nd through 8th "dan" black belts.  As one of the first graduates of the Japan Karate Association (JKA) Instructors' Training Program in 1959, he has played an important role in the growth of JKA karate and the internationalization of Shotokan karate.  Yaguchi first arrived in the United States on June 5, 1965, and continues to reside in the US to the present day.  In 1974, Yaguchi founded the ISKF of Colorado, the regional headquarters for the Mountain States Region. The Calchaquí Valley (Spanish: Valles Calchaquíes ) is an area in the northwestern region of Argentina which crosses the provinces of Catamarca, Tucumán, Jujuy and Salta.  It is best known for its contrast of colors and its unique geography that ranges from the mountain desert to the subtropical forest. The Morristown Twins (previously known as the Maryville-Alcoa Twins) were a minor league baseball team that played in the Class D and Class C Mountain States League from 1953 to 1954.  They were originally located in Maryville and Alcoa, Tennessee, and played their home games at Hunt Field in Maryville.  The Twins won the 1953 Mountain States League pennant by finishing the season in first place.  In 1954, the Twins relocated to Morristown, Tennessee, where they became the Morristown Twins. The gilded flicker ("Colaptes chrysoides") is a large-sized woodpecker (mean length of 29 cm ) of the Sonoran, Yuma, and eastern Colorado Desert regions of the southwestern United States and northwestern Mexico including all of the Baja Peninsula except the extreme northwestern region.  Golden yellow underwings distinguish the gilded flicker from the northern flicker found within the same region, which have red underwings. The Mountain States (also known as the Mountain West and the Interior West) form one of the nine geographic divisions of the United States that are officially recognized by the United States Census Bureau.  It is a subregion of the Western United States.  The Mountain States are usually split up into two other regions known as the Northwest and Southwest.  Idaho, Montana, and Wyoming are considered part of the Northwest, while Arizona, Colorado, Nevada, New Mexico, and Utah are considered part of the Southwest. Montana is a state in the northwestern region of the United States.  The state's name is derived from the Spanish word "montaña" (mountain).  Montana has several nicknames, although none official, including "Big Sky Country" and "The Treasure State", and slogans that include "Land of the Shining Mountains" and more recently "The Last Best Place". The National Bison Range Complex includes four National Wildlife Refuges and the Northwest Montana Wetland Management District, and is located in the northwestern region of Montana in the northwestern United States. This is a list of companies based in Idaho.  Idaho is a state in the northwestern region of the United States.  It is the 14th largest, the 39th most populous, and the 7th least densely populated of the 50 United States.  The United States Census Bureau estimates that the population of Idaho was 1,654,930 as of July 1, 2015, up from 1,595,728 on July 1, 2012, a 1.8% increase since 2010.  The state's largest city and capital is Boise.  Today, the largest industry in Idaho is the science and technology sector.  It accounts for over 25% of the state's total revenue and over 70% of the state's exports.  Idaho's industrial economy is growing, with high-tech products leading the way.  Idaho is an important agricultural state, producing nearly one-third of the potatoes grown in the United States.
Answer: Idaho, Montana, and Wyoming