Apache is one of the larger independent, non-integrated oil companies, and one of dozens that are based around Houston. These companies focus on exploration and development of oil and gas fields, generating their profits primarily as leaseholders. They generally have dozens or hundreds of properties all over the world, and employ a few thousand people, and generate a few billion in annual revenue. Apache was founded in Minneapolis in 1954, and grew by acquisitions, especially the MW Petroleum assets it acquired from Amoco in 1991, which prompted the company's move to Houston.