Tropical maize lines originating from low latitude environments are very photoperiod sensitive, which is a fundamental block when trying to breed with tropical maize lines in temperate environments. Although several studies have been done to understand the physiology of maize photoperiod sensitivity, there are only 2 clear-cut maize photoperiod studies. Our research will use four populations to identify quantitative trait loci (QTL) that are consistent and unique between different tropical maize lines. We will use 2 growing locations at different latitudes to show how photoperiod affects the days to flowering, total leaf number, and plant height of our populations. With this data, we will identify the QTL that produce photoperiod sensitivity in multiple maize populations. We have thus far identified a single QTL region that is consistent across all populations from this study and across the 2 populations from the previous studies. Fine-mapping and BAC walking may be applied to this region in order to clone the gene(s) responsible for this trait. This study will be help breeders select photoperiod insensitive lines for development in temperate regions.