With a total area of 121,590 square miles (314,900 km2), 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 miles (3.5 kilometres) 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, Arizona, and Utah come together at the Four Corners in New Mexico'