Title: Montana
Content:   Montana is one of the eight Mountain States, located in the north of the region known as the Western United States. It borders North Dakota and South Dakota to the east. Wyoming is to the south, Idaho is to the west and southwest, and the Canadian provinces of British Columbia, Alberta, and Saskatchewan, are to the north, making it the only state to border three Canadian provinces. With an area of 147040 sqmi, Montana is slightly larger than Japan. It is the fourth-largest state in the United States after Alaska, Texas, and California; it is the largest landlocked state.
Title: Western Montana
Content:  Western Montana is the western region of the U.S. state of Montana. The most restrictive definition limits western Montana only to the parts of the state west of the Continental Divide. Other common definitions add in the mountainous areas east of the divide including Beaverhead, Gallatin, Jefferson, Lewis and Clark, Madison, and Park Counties. The region is sometimes considered to be part of the Inland Northwest.
Title: 34th meridian west from Washington
Content:  The meridian was first used as a boundary when the Montana Territory was created in 1864. It served as Montana Territory's extreme southwestern boundary. The next usage of the boundary came when the Wyoming Territory was established in 1868, with the meridian as its western boundary. It was also at this time that it became much of the then-Idaho Territory's eastern boundary, as well as the extreme northeastern boundary of the then-Utah Territory. Montana became a state in 1889, with Idaho and Wyoming following the year afterwards. Utah became a state in 1896.
Title: Outline of Montana
Content:  The following outline is provided as an overview of and topical guide to the U.S. state of Montana: Montana &ndash; fourth most extensive of the 50 states of the United States of America. Montana is the northernmost of the western Mountain States. The Territory of Montana joined the Union as the 41st state on November 8, 1889.
Title: Outline of Montana
Content: Montana is: a U.S. state, a federal state of the United States of America ; Location: ; Northern hemisphere ; Western hemisphere ; Americas ; North America ; Anglo America ; Northern America ; United States of America ; Contiguous United States ; Canada–US border ; Western United States ; Mountain West United States ; Northwestern United States ; Population of Montana: 989,415 (2010 U.S. Census ) ; Area of Montana: ; Atlas of Montana Geography of Montana
Title: Montana
Content:  Montana is a state in the Mountain West subregion of the Western United States. It is bordered by Idaho to the west; North Dakota and South Dakota to the east; Wyoming to the south; and by the Canadian provinces of Alberta, British Columbia, and Saskatchewan to the north. It is the fourth-largest state by area, the seventh-least populous state, and the third-least densely populated state. The western half of Montana contains numerous mountain ranges, while the eastern half is characterized by western prairie terrain and badlands, with smaller mountain ranges found throughout the state. In all, 77 named ranges are part of the Rocky Mountains. Montana has no official nickname but several unofficial ones, most notably "Big Sky Country", "The Treasure State", "Land of the Shining Mountains", and "The Last Best Place". The economy is primarily based on agriculture, including ranching and cereal grain farming. Other significant economic resources include oil, gas, coal, mining, and lumber. The health care, service, and government sectors are also significant to the state's economy. Montana's fastest-growing sector is tourism; nearly 13 million annual tourists visit Glacier National Park, Yellowstone National Park, Beartooth Highway, Flathead Lake, Big Sky Resort, and other attractions.
Title: Washington (state)
Content:  Washington is the northwesternmost state of the contiguous United States. It borders Idaho to the east, bounded mostly by the meridian running north from the confluence of the Snake River and Clearwater River (about 117°02'23" west), except for the southernmost section where the border follows the Snake River. Oregon is to the south, with the Columbia River forming the western part and the 46th parallel forming the eastern part of the Oregon–Washington border. During Washington's partition from Oregon, the original plan for the border followed the Columbia River east until the confluence with the Snake, and then would have followed the Snake River east; this was changed in order to keep Walla Walla's fertile farmland in Washington. To the west of Washington lies the Pacific Ocean. Its northern border lies mostly along the 49th parallel, and then via marine boundaries through the 
Title: New Mexico
Content:   With a total area of 121590 sqmi, New Mexico is the fifth-largest state, after Alaska, Texas, California, and Montana. Its eastern border lies along 103°W longitude with the state of Oklahoma, and 2.2 mi west of 103°W longitude with Texas (due to a 19th-century surveying error). On the southern border, Texas makes up the eastern two-thirds, while the Mexican states of Chihuahua and Sonora make up the western third, with Chihuahua making up about 90% of that. The western border with Arizona runs along the 109° 03'W longitude. The southwestern corner of the state is known as the Bootheel. The 37°N parallel forms the northern boundary with Colorado. The states of New Mexico, Colorado, 
Title: 39th meridian west from Washington
Content:   The 39th meridian west from Washington is an archaic meridian based on the Washington meridian. The meridian is used as a boundary for two states. The first and only usage of the meridian as a boundary occurred in 1864. In that year, the Montana Territory was created from Idaho Territory with the meridian serving as its extreme northwestern boundary. Montana became a state in 1889, with Idaho following the next year.
Title: Mountain states
Content:  The Mountain West is one of the largest and most diverse regions in the United States. Most regional boundaries of the Mountain West are often looked at the area from the High Plains to the Sierra Nevada and the Cascade Range. The southern and northern portions of the Mountain West are often split into two separate regions. The southern portion (Arizona and New Mexico) is often called the Southwest region, while the northern portion (Idaho and Montana) is often included in either the Northwest states or called the "Northern Rockies".

Question: what us state forms the western boundary of montana?
Answer: Idaho.