once thought to face extinction as a race or culture, native americans of numerous tribes have achieved revival of aspects of their cultures, together with asserting their sovereignty and direction of their own affairs since the mid-20th century. many have started language programs to revive use of traditional languages; some have established tribally controlled colleges and other schools on their reservations, so that education is expressive of their cultures. since the late 20th century, many tribes have developed gaming casinos on their sovereign land to raise revenues for economic development, as well as to promote the education and welfare of their people through health care and construction of improved housing.