The Great Plains contain many of the best-known Paleoindian sites in North America, and a number of these localities were key to determining the chronology of Paleoindian occupations in the years before, during, and since the development of radiocarbon and other chronometric dating methods. Initial attempts at dating were based on correlation with extinct fauna, the "geologic-climatic" dating method, and stratigraphic relationships of artifacts within sites. By the time radiocarbon dating was developed (1950), the basic Paleoindian sequence (oldest to youngest) was: Clovis-Folsom-unfluted lanceolates (such as Plainview, Eden, and Scottsbluff). Initial applications of radiocarbon dating in the 1950s did little to further resolve age relationships. In the 1960s, however, largely through the efforts of C. V. Haynes, a numerical geochronology of Paleoindian occupations on the Great Plains began to emerge On the Southern Great Plains the radiocarbon-dated artifact chronology is: Clovis (11,600-11,000 yr B.P.); Folsom and Midland (10,900-10,100 yr B.P.); Plainview, Milnesand, and Lubbock (10,200-9800 yr B.P.); Firstview (9400-8200 yr B.P.); St. Mary's Hall, Golondrina, and Texas Angostura (9200-8000 yr B.P.). The chronology for the Northern Great Plains is: Clovis (11,200-10,900 yr B.P.); Goshen (ca. 11,000 yr B.P.); Folsom (10,900-10,200 yr B.P.); Agate Basin (10,500-10,000 yr B.P.); Hell Gap (10,500-9500 yr B.P.); Alberta, Alberta-Cody (10,200-9400 yr B.P.); Cody (Eden-Scottsbluff) (9400-8800 yr B.P.); Angostura, Jimmy Allen, Frederick, and other parallel-oblique types (9400-7800 yr B.P.). Fifty years after the development of radiocarbon dating, the basic typological sequence has not changed significantly except for the realization that there probably was significant temporal overlap of some point types, and that the old unilinear sequence does not account for all the known typological variation. The chronology has been continually refined with the determination of hundreds of radiocarbon ages in recent decades.