Koster is situated on colluvial fans and located 8 km northeast of Hardin in Greene County, Illinois. Carbonized maize cupules, kernels, and glumes were identified in nine flotation samples representing four cultural horizons (9D to 9A), and two of these were dated, providing, what was at the time, a pioneering use of the AMS radiocarbon method to directly date maize (Conard et al. 1984:444).
| ID | Other ID | Type | Subtype | Uncal BP (years) | ± 1 σ (years) | Median cal BP (years) | Lower cal BP (years) | Upper cal BP (years) | δ13C | Contaminated? |
|---|---|---|---|---|---|---|---|---|---|---|
| 632 | NSRL-295 | MacroSample | unknown | 250 | 300 | 321 | 729 | 0 | No | |
| 633 | NSRL-296 | MacroSample | unknown | 600 | 40 | 601 | 656 | 539 | No |