Using horses in the early-18th century, the Comanche left a semi-desert homeland west of the Rocky Mountains and moved into the southern plains. In sweeping south and eastward, they dislodged various Apache groups. The Comanche were organized into at least 11 independent bands, each with its own chief and territory. Expert horsemen, they supplemented their buffalo-hunting economy with trade in horses, mules, and captives obtained in raids against white settlements in Texas and New Mexico. The Comanche may have had a population of up to 20,000 in the late-18th century, but were reduced to 1,500 by 1910.