The Mid-continent oil field is a broad area containing hundreds of oil fields in Arkansas, Kansas, Louisiana, New Mexico, Oklahoma and Texas. The area, which consists of various geological strata and diverse trap types, was discovered and exploited during the first half of the 20th century. Most of the crude oil found in the onshore mid-continent oil field is considered to be of the mixed base or intermediate type (a mix of paraffin base and asphalt base crude oil types).