It was named by Cynthia Irwin-Williams in the 1960s for those areas: Pinto Basin (PI), Cochise tradition (CO), and San Jose (SA), which together are called "Picosa".
[1] Chiricahua Cochise tools include a variety of projectile points and many seed-processing artifacts.
By this time, the Archaic population of the American Southwest appears to have grown, with groups exploiting a wider range of environmental zones and sometimes living in larger, perhaps more permanent, settlements.
Some San Pedro sites contain oval pithouses excavated about 1.6 feet (0.49 m) below ground level.
Such dwellings would require considerable effort to build, which would indicate a longer term of occupation.