The use of the meridian as a boundary began in 1863 when the Idaho Territory was created, with the 27th meridian as its eastern boundary.[4] At that time, the Dakota Territory and the Nebraska Territory gained their western boundary as portions of those territories were made a part of Idaho Territory. Nebraska became a state in 1867.[5] In 1868, the Wyoming Territory was created with the meridian as its eastern boundary.[6] The Dakota Territory was divided into North Dakota and South Dakota when they became states on November 2, 1889, and Montana became a state just six days later.[7][8] Wyoming became a state in 1890.[9] The Montana-North Dakota, Montana-South Dakota, Wyoming-South Dakota, and Wyoming-Nebraska state borders therefore are all defined by the 27th meridian west from Washington.[10]
