There were two goals to be achieved from the analysis of 53 skeletonized infants from the Southwest Collection at the National Museum of Natural History. The first objective was to determine whether this infant sample could be aged based on a mandibular measurement. The second was to determine which dimension of the mandible, if any, most accurately predicts infant age within a six-month range. Seven osteometric measurements were applied to each mandible. Statistical analysis determined that the individuals in the Smithsonian's Southwest Collection that were under two-years-old could be accurately aged to within six months. Out of these seven measurements the most accurate age-at-death estimates were generated based on the maximum height of the mandibular ramus. This finding can potentially aid investigators in determining the age-at-death of infants.